This is the character page for Bunsen Is a Beast.
- Bunsen (Jeremy Rowley) is a beast who becomes friends with Mikey and is the first beast to become a student in a human school. His body is a bit cyan, light blue, and white, with magenta-colored lips, arms, and legs. He is very often seen with a smile. He is very cute and fun-loving.
- Mikey Munroe (Ben Giroux) is Bunsen's best friend, who guides him through the human world. He attends Flap's class along with Amanda and deals with the troubles that arise between them.
- Amanda Killman (Kari Wahlgren) is a blossoming ingénue clad in a red, white, and blue schoolgirl uniform and is Bunsen's nemesis. She is constantly scheming to get rid of Bunsen by trying to prove that beasts and humans can't coexist. She speaks with a lateral lisp and wears dental braces. Mikey, who stands in the way of this, has become her enemy, although she has a secret crush on him, as hinted in several episodes where she has made comments on him such as praising his tan and shorts. She likes boys in gym shorts, men in tanks or uniform, and her toys Princess Sassafrass and Queen Elizabear. She has a rich father who controls the school board, and can afford a water tower full of acne cream and bribes for townsfolk. She has a pet kitten named Doctor Revenge, who was given to her by Mikey and Bunsen.
- Beverly (Kari Wahlgren) is Amanda Killman's #1 henchman/second in command and seems to be willing to do anything Amanda commands. She, at times, is sometimes smarter than Amanda, sensing danger ahead as Amanda mostly ignores her.
- Darcy (Cristina Milizia) is a home-schooled and socially odd friend of Bunsen and Mikey, who occasionally tags along with them on their adventures.
- Sophie Sanders (Kari Wahlgren), a preening, flamboyant cool girl who speaks in a valley girl accent, and is one of Amanda Killman's greatest nemeses as well as her arch-rival in Mikey's affection. Mikey has a secret crush on her.
- Tooth Fairy (Tara Strong), the jolly-happy fairy queen, who gives money to children who have lost their teeth.
- Big Mikey (Jeff Bennett), a black bear that Bunsen found and named after Mikey.
- Doctor Revenge, a white kitten that Bunsen discovers and gives to Amanda Killman.
- Jerk Von Handsome (Jeremy Rowley), a Swedish foreign exchange student who likes looking at himself in his mirror.
- Liz, the sister of Commander Cone, whom he left alone in her basement doing his laundry.
- Hugging Chair, Bunsen's chair who first appeared in "Hug It Out'ch", at first it trapped Amanda and wouldn't let her go, but in the end, Bunsen makes Amanda happy, and the chair releases her.
- Anti-Claus, is a supervillain king who is 1,000 years old plans to destroy Christmas.
- Miss Flap (Cheri Oteri), is a middle-aged lady who teaches Bunsen's class.
- Commander Cone (Jerry Trainor), is a character who first appeared in "Bunsen Screams for Ice Cream" to help Amanda expel Bunsen from school by tempting him with his truck, but Mikey keeps Bunsen under control in the end. He reappears in "Astro-Nots", where Bunsen and Mikey see him in MASA and mistake him for a Mastronaut, so he gives them a tour, but accidentally launches them into space. In the end, Cone is no longer an ice cream vendor; he is a MASA Alien Space Defender. As noted several times, he pines for his ex-girlfriend Vanessa to return to him.
- Vanessa is Commander Cone's ex-girlfriend. According to Cone, she broke up with him on his birthday, Christmas Eve, after he became an ice cream vendor.
- Aunt Shannon (Matilda Zielger) is Mikey's evil guardian.