Jet Mender is the adorable best friend of Halley Vivian and acts as the series' deuteragonist (in Astroblast in Paris: The Movie, however, he serves as the protagonist). Jet's mother Carrie died from an illness when Jet was a few months old. In Astroblast in Paris: The Movie, his father, Robert was going to marry Coco, an evil woman who hates children, and tries to get Robert to fall in love with her, but in the end, Robert fell in love with and married Chloe, Jade's mother. His beautiful new mother is loving and caring, just as his father. Jet also has a puppy named Precious (also known as Sparky) and a poodle named Cindy. Jet was 2 years old in Astroblast, 11 years old in the All Grown Up! pilot episode All Growed Up and 12 years old in Astroblast: All Grown Up! series itself.
In every crowd there's a worrywart, and among the babies it's Jet Mender. Halley's best friend Jet is a likable two-year-old scaredy cat who sees monsters in every closet and worries about a hundred ways things can go wrong. Halley's adventurous schemes often reduce Jet to shivers "M-m- maybe this isn't such a good idea," he'll suggest, as the babies are off to sneak into the dark and dank garage. But since Jet also hates being left behind, he trudges along warily. And in the process, he often surprises himself with the courage he summons up. Like his dad, Robert. Jet never forgets that every silver lining comes with a cloud attached. - Astroblast Description from Sprout.
Jet has changed in many ways since he was a baby. For one thing, he isn't as scared of the world as he once was, and is even willing to take a risk now and then! He now likes girls, and will go to great lengths to get their attention, including dressing up like a foreign exchange student or being nice to Sputnik. Jet is still best friends with Halley, and often turns to her for advice. Although Jet may not be the scaredy cat he used to be, his personality hasn't changed much at all! - Astroblast: All Grown Up! Description from Sprout.
Despite his cuteness, Jet is pessimistic and scares easily, and at the first suggestion that he and the other babies should do something or go somewhere, he will always say, "Maybe this isn't such a good idea." All the same, he's still best friends with Halley, Comet and Venus). Among his fears are adventures, cats, losing his hat, germs, bad things happening to his friends, clowns, and the "guy on the oatmeal box with the scary hat" (a parody of Quaker Oats). He is loyal and often brave, facing his fears briefly to come through for his friends, whenever there's a problem, Jet's there to help his friends get through it emotionally. Jet doesn't really like misbehaving, but his friends often get him into trouble by accident. He is very close to his father Robert, and is usually the main target of Sputnik's bullying. Jet was the only character who did not come from a two-parent household before the remarriage. It is revealed in the episode The Alien that Jet has an outie belly button, and is revealed to be left-handed in Jet's a Lefty. Things had changed for Jet in Astroblast in Paris, when he got A new sister named Jade Mender, and a new mother named Chloe Mender.
In Astroblast: All Grown Up!, Jet is still timid, but he is a bit more of a risk taker. He has trouble lying to others and still appears to be the voice of reason.
Jet is an alligator who wears an orange hat, an orange long sleeve shirt, white shorts, diapers and partially untied blue shoes with white laces. Since after Jet vs. The Potty, he wore white bear patterned, light blue, or beige training pants. Afterwards, he wore dark blue or white briefs.
As he gets older, He loses his buck teeth and gains braces, and he now wears a black hat instead of an orange one. He usually wears a watch on his right wrist. In All Growed Up, he wore a light blue button-up shirt with a picture of saturn on the top right corner, green baggy pants, and blue and white sneakers. He wears a similar outfit in the first few episodes of Astroblast: All Grown Up, but his shirt is green, his pants are orange, and his shoes are purple. He later switches to a brown sweater with a sea green undershirt, purple pants, and green sneakers. He wears this for the rest of season 1. In Season 2 and onwards, he changes his outfits a lot, but his primary outfit consists of a purple t-shirt over a yellow long-sleeved shirt, green pants, and blue sneakers.
Jet Mender has appeared in most episodes of Astroblast and Astroblast: All Grown Up!. His first appearance was in Halley's First Birthday. His last appearance was in Brothers Grimm from Astroblast: All Grown Up!.
Robert Mender - Robert is Jet's father. They are very similar as they are both scaredy cats and have allergies. They both are allergic to dandelions. They are also both friendly. Robert is very protective of Jet after the death of his wife Carrie (Jet's mother).
Carrie Finster - Carrie is Jet's late biological mother. Jet doesn't remember her too well but he does remember her when he was really young, saying he has dreams about her (though he doesn't know who she is in his dreams, he just thinks its a nice and pretty lady) Jet had seen what she looked like in a photo in the Mother's Day episode as Robert told him about her.
Chloe Mender - Chloe was Jet's stepmother until she legally adopted him. Jet didn't like the way Chloe did things at first and got upset, especially when she fixed his Wawa because she put sparkly blue eyes on him (also because Wawa was a gift from his mother). However Chloe and Jet now get along as she says she'll learn more about the things he does and the way he likes things done.
Jade Mender - Jade was Jet's step-sister until she was legally adopted by Robert Mender. Jet loves Jade and tries to protect her, when he can, from getting hurt or in danger. In Astroblast: All Grown Up! Jet is still somewhat protective of Jade, as he tries to protect her from Duke, the school's bad boy. Jet also got upset when the gang found Halley and Jade's intials carved in the wall of the Mender garage in HV+JM, as he tells Halley that it wasn't cool to "mack on his best friend's sister". The intials carved into the wall caused Halley and Jet to not only temporarily break off their friendship but for Jet to be suspicious of Jade. However, he does it all because he is her older brother and wants to make sure she is safe.
Halley Vivian - Halley is Jet's best friend that he met when Halley was only eight days old. In A Step at a Time, Jet learned that he was the reason that Halley walked for the first time and that they've been friends ever since then. Despite trying to talk Halley out of it, Jet always goes on the scary adventures that Halley leads him on. Some of the adventures cause Halley and Jet to argue like in the episodes: Opposites Attract and Farewell, My Friend; however they always make up in the end. In the Astroblast: All Grown Up episode HV+JM, Jet got upset with Halley when he thought that Halley was spending so much time with Jade, that she forgot about him, up until the point they fought and broke off their friendship. However, after Halley came running to his house scared, and they sat down and talked, Jet and Halley patched things up with each other.
Comet Grinner and Venus Grinner - Jet is good friends with the twins, but gets grossed out by things they say and do. And he may have a crush on Venus, as seen in I Do. She may return it, as implied in The Mender Who Stole Christmas.
Frogerina Jones - Jet and Frogerina are very good friends. It is hinted that the pair may possibly, though not confirmed, like each other, as Jet asked Frogerina to be his date in Junior Prom and she accepted, while in It's Cupid, Stupid, Frogerina asks Jet to go to the Valentine's Day dance with her, and he agrees to it.
Lola Boscarelli - Lola is Jet's love interest in Astroblast: All Grown Up! as seen in Jet's in Love and It's Cupid, Stupid. When Lola is around Jet's presence, he gets nervous and doesn't know how to act. They both enjoy the same smoothies and Lola likes an individual who is sweet-hearted and truthful. Ever since the Chongo incident, both Jet and Lola have talked to each other on several occasions and even danced with each other in the gymnasium for Valentine's Day.
- Jet's character design was originally intended to be used for a bully, and was based on one of the main music composers for the series, Mark Mothersbaugh.
- Chloe legally adopts Jet as her son in Menderella and Robert legally adopts Jade as his daughter. In a legal sense, that technically makes Jet and Jade siblings and not just step-siblings.
- In Season 1 to early episodes of Season 2, Jet is shown with multiple teeth besides his trademark buckteeth. However since Showdown at Teeter-Totter Gulch, those multiple teeth were eliminated.
- 12 year old Jet kept his appearance Astroblast: in All Grown Up!.
- In All Growed Up (where 11-year-old Jet appeared), 12 year old Sputnik introduces him to 12 year old Samantha Shane as "Jet Mender II," even though his grandfather's name is Greg.
- The Behind the Scenes featurette for Astroblast in Paris shows that Jet was originally going to sing "I Want a Mom" himself, but this idea was scrapped in favor of having the song performed by Cyndi Lauper.
- He was played by Christine Cavanaugh, who also voiced Oblina, in another Sproutoon, Real Monsters. Coincidentally, Oblina appeared in the episode Ghost Story.
- As seen in the Season 4 episode "Radio Daze", Jet is shown to be ticklish on his feet.
- It is unknown if Jet has any cousins. On his father's side, he doesn't because Robert is an only child, and Jet's grandparents always remark how Jet is their only grandchild, and happily cry when Robert adopts Jade since that means they have two grandchildren now.
- It is possible that Jet's birthday is either in late April or early May, if Halley's birthday is in June. If Halley's birthday is in August, Jet would be born around June 14. If Halley's actual birthday is in June, since in Astroblast: All Grown Up Jet mentions that he's a year, 1 month, 3 weeks and 5 days older than Halley which would make his birthday fall around late April or early May. Since Comet and Venus are 3 months older than Halley and their birthday is March 31st along with the fact that Halley was born 2 months premature, making Halley's actual birthday in June but her real birthday is supposed to be in August, and according to what Jet said would make his birthday most likely fall in late April.
- In Astroblast: All Grown Up! episode Truth or Consequences, Jet has been seen as a 3-4 year old, and a 7-8 year old.
- Jet, in Astroblast: All Grown Up, has freckles on his bottom, as briefly revealed in What's Love Got To Do With It?
- Jet is allergic to dandelions like his father, but not cats.
- Sputnik calls him by his last name sometimes, starting in Season 3.
- He didn't want to give up his diapers, but now that he is potty trained, he refuses to wear them again.
- His first word heard by the grown-ups was "no", as was shown in Astroblast in Paris: The Movie.
- Apparently, because of Jet's nose always being congested and stuffed up, because of allergies, he doesn't know what Comet and Venus smell like, except in the episode The Smell of Success when he had his nose unstuffed and actually could detect the stinky smell coming from the twins.
- Jet is similar to Jeremie Belpois from Code Lyoko. They're both smart, aren't good at P.E., and want to skip P.E. although Jet doesn't skip gym class.
- After watching Captain Blasto, he takes a nap.
- Jet is terrified of clowns like Olivia Vivian.
- In Dude, Where's My Horse?, it's revealed that Jet can play the harmonica, although he never says how.
- Despite being one of the oldest members of the group, Jet has never had his first kiss.
- In Astroblast in Paris: The Movie, Jet said "9/11".
- He my have a crush on Venus, as seen in "I Do".
- Jet is revealed to be very good at sewing as seen in "HV+JM", where he makes a two-headed dragon costume (for him and Halley) on his own.
- It is revealed that Jet is great at climbing as seen in "Interview With a Campfire".
- Jet is shown to be very protective of his sister Jade as it has been shown in a lot of episodes in both Astroblast and Astroblast: All Grown Up!.
- According to Jet in "Super Hero Worship", he started to read when he was five years old.
- Jet's favorite superhero is "Armadillo Dave".
- He relates to him because Armadillo Dave is also slow, klutzy, and near-sighted.
- In "HV+JM" Jet reveals he wet his bed until he was 7 years old to Halley.
- In "Bad Blood", Jet suffers from a skin condition known as psoriasis.
- Halley sometimes calls Jet, Jetaroo in Astroblast, while Caroline calls him Jetster, as do the others later in Astroblast: All Grown Up!.