Kermit the Frog is a Muppet character who has appeared in promotional material for Amphibia. He first appeared in two videos promoting the show, "Kermit Reacts to Amphibia" where he reacts to the opening sequence and "Kermit the Frog (Consultant)" where he works on the show as its "unofficial frog consultant."
Kermit appeared at the 2019 D23 Expo where he hosted a Q&A panel for Amphibia and Big City Greens. During the panel, Matt Braly lets Kermit look at a live version of the Calamity Box. However, Kermit opens it and gets teleported to Amphibia. He initially enjoys it there, but that quickly ends when he spots a frog-eating moth and heads back to the Expo. He ends up at Big City from Big City Greens on the way.
- Frogs in Amphibia have commonly appeared with hair. Ironically, in the first season of Sesame Street, Kermit did a lecture on hair where he constantly and firmly emphasizes how "frogs don't have hair."
- Kermit states that he grew up in a swamp similar in appearance to Amphibia, "only wetter, muddier, and closer to the Interstate."
- A drawing of Kermit appeared on a cologne produced in 1995 also called "Amphibia." According to Matt Braly, a reference to the cologne would have been made in "Kermit the Frog (Consultant)", but it was cut out for time.
- Kermit is the second Muppet to voice a character in a Disney animated series, the first being Fozzie Bear, who voiced Dr. Enamel in Big City Greens.