On a scale of one to ten, sixth-grader Danvers Blickensderfer's life is a solid minus two. But he really hits rock bottom when he auditions for the local talent show: his death-defying hula-hooping-ninja tribute to Gonzo the Great is beat out by the world's most obnoxious middle school boy band, Emo Shun.
With his daredevil dreams dashed, Danvers goes to bed... and wakes up feeling a little fuzzy-literally! He's turned into a Muppet!
Danvers Blickensderfer: the protagonist and narrator. He has a pet rat named Curtis, and a little sister named Chloe (aka "evil"). His all-time idol and hero is Gonzo. Danvers loves to perform ridiculous stunts and escape tricks with the help of his reluctant assistant and best friend Pasquale. One night before falling asleep, Danvers wishes he were like Gonzo, and the next morning he discovers that he has turned into a Muppet. With the unexpected help of his sister, he ends up getting his dream job at the Muppet Theater.
Pasquale Arrelano: Danvers' best friend, and the safety assistant for Danvers' stunts. At first, Pasquale participates in the stunts, but after he's hurt several times, his parents make Danvers sign a contract to not cause any form of bodily harm to him. When Danvers becomes a Muppet, he begins spending more time with the Muppets than his best friend, and Pasquale feels unhappy that he is ignored. After seeing Pasquale say this on TV, Danvers goes to apologize and invites him to participate in the Mon Swoon act of the Fall on Ice Festival.
Chloe Blickensderfer: Danvers' five-year-old sister. Danvers does not like Chloe and secretly thinks of her as "Evil Incarnate." When Danvers turns into a Muppet, she sends his story to the Muppet Theater and gets him his dream job, the first nice thing she ever did for him. Danvers pays her back by allowing her to take down his Gonzo posters and put up posters of her own favorite thing, "The Fluffleberries".
Curtis: Danvers' pet. He is good friends with Pasquale, but is a little too fond of Danvers' new Muppet look. Dr. Bunsen Honeydew zaps him with the SHAMPUZ laser, which makes him a giant. Animal calls him "raccoon".
Mr. Piffle: Danvers' teacher.
Button Hauser: Danvers' classmate in Mr. Piffle's class. Button presents an oral report on her hero, "the innocent smile of a child". Danvers finds Button's choice nauseating.
Dante Digarmo: Danvers' classmate. Dante gives his oral report on his "all-time idol," Kermit the Frog. He is the only other student, besides Danvers, to do a report on a Muppet.
Coach Kraft: Danvers' gym teacher. He constantly tortures Danvers in gym class.
Hockney: a pig student at Eagle Talon Academy. He and Danvers Blickensderfer are chosen for internships with the Muppets.
Mr. Mallard: Danvers' school counselor.
Emo Shun: Coldrain Middle School's most popular boy band. The band includes three sixth graders: the three-foot-tall Cody Carter, the French-speaking Danny Enfant, and the leader, singer Kip Strummer. The band produces a "sappy, schmaltzy" music video for their single "Hey Girl" which they posted online.
Mon Swoon: Danvers Blickensderfer's boy band. There's Danvers as lead singer, Teddy B and Orange Sherbet as backup singers and dancers, Animal on drums, Shrimp Scampi as unknown and Pasquale Arrelano as safety supervisor.
Danvers performs his tribute to Gonzo while Mr. Piffle looks on.
Block City is the city in which Tales of a Sixth-Grade Muppet takes place. Its schools are Coldrain Middle School (which Danvers Blickensderfer attends), a preschool his sister Chloe goes to which is not referred to by name, and Eagle Talon Academy, run by Sam the Eagle. It has a newspaper, the Block City Beat, and the yearly Fall on Ice Festival.
Block City Beat is Block City's newspaper. Its name is only shown in its first appearance, in which Danvers' dad is reading it at the table, and it reports the headlines "Strange Green Flash Seen Last Night" (referring to the green flash that probably caused Danvers to mutate into a Muppet) and "Jobs? What Jobs?" In its second appearance, somebody is reading it at Veteranarian's Hospital, and it contains an ad for the Fall on Ice Festival and an article reporting Danvers' transformation. In its third appearance Danvers' dad has it again on the couch while watching Chloe, and it says "Pigs in Space", and "Jobs? Hah!" In its fourth and final appearance, it says Sundays have been officially declared Disco Pirate Day by the mayor (Danvers already had Sunday as his disco pirate day, and the disco pirate costume he's wearing implies that it is Sunday).
Eagle Talon Academy is a school run by Sam the Eagle, and the temporary location for Muppet Labs. Danvers and Pasquale go there to find the source of the mysterious Muppetmorphosis. Working there also is the Swedish Chef, and the students there who they talk to are Hockney, a carrot, Ingy, and Minette.