Frogs are amphibians featured in many Muppet productions.
The best known Muppet frog is, of course, Kermit. Originally designed as an abstract lizard-like creature in 1955, he was referred to as a frog on several occasions during the late 1960's (including The Muppets on Puppets). In following productions (Hey Cinderella, Sesame Street), he was given webbed feet and a collar, and referred to as "Kermit the Frog".
In 1971, a group of frogs similar to Kermit -- yet without collars and stripes for pupils -- was built for the TV special The Frog Prince. The leading character, a tiny frog named Robin who used to be a prince, would return on The Muppet Show as Kermit's nephew and became one of the main characters. The other green-and-blue frogs would pop up in various different Muppet productions; they functioned as a frog chorus/orchestra in The Muppets Valentine Show (1972), and formed singing groups and a troupe of Frog Scouts on The Muppet Show.
A group of frogs was also seen in the 1990 special The Muppets at Walt Disney World, as Kermit's relatives in Paradise Swamp. Their latest appearances included Billy Bunny's Animal Songs (1993) and Kermit's Swamp Years (2002). In the latter, they appear as Kermit's brothers and sisters, and a separate clan of frogs are seen later in the pet store. One blue frog can be spotted in The Muppets.
One frog seen in The Frog Prince had an eye mechanism which allowed his eyes to bulge.
During the first years of Sesame Street, frogs were portrayed by green or pink Anything Muppets with bulgy eyes; during later seasons, more defined frog puppets were used, with a more accurate physique. By the 1980s, some previous frog puppets used in The Muppet Show and other productions crossed over and were used on Sesame as well.
One four-limbed frog was used as the titular "Caribbean Amphibian" (Kevin Clash). The puppet was also featured in the chorus of musical numbers such as "African Alphabet" and "We Are All Earthlings" (in both the original and the remake with Jill Scott); and was seen in an Ernie and Bert Sketch (performed by Joey Mazzarino, speaking only in "nee-deep"s).
A similar looking frog named Froggy (after the song "Froggy Went A Courtin'") was seen in the home video Kids' Favorite Country Songs. Other frogs, old and new, congregated in "The Frogs in the Glen."
A toad and a frog were seen in the song "Let's Lay an Egg" singing about their egg-laying powers.
Frogs from other Muppet productions include Doc Bullfrog from Emmet Otter's Jug Band Christmas; Bill, Gil and Jill from The Muppets Take Manhattan; Goggles, Croaker and Blotch from Kermit's Swamp Years; and a realistic frog that made appearances on The Animal Show and Mopatop's Shop. Real frogs appeared an episode of Fraggle Rock.
(This list includes frogs and toads, as in taxonomy, no distinction is made between the two.)