Kermit the Frog is a Muppet and one of puppeteer Jim Henson's most famous creations. Kermit was performed by Henson until his death in 1990. Since then, he has been performed by puppeteer Steve Whitmire.
An early version of Kermit appeared in 1955, in a five minute puppet show for WRC-TV Sam and Friends. The prototype Kermit was created from a green ladies' coat that Henson's mother had thrown in the trash can, and two ping-pong balls for eyes. The early Kermit was a sort of lizard-like creature; Kermit's first appearance as a frog was in the television special Hey Cinderella in 1969, and he's been a frog ever since.
Kermit had his big break in 1971, with frequent appearances on Sesame Street as a news reporter interviewing nursery rhyme characters. One of his most memorable works was the song "Bein' Green". Kermit's song "The Rainbow Connection" was also a big hit from The Muppet Movie and has become the signature song of The Jim Henson Company. (It is also the only movie song sung by a frog to be nominated for an Academy Award.)
To date he is a world wide phenomenon there are very few people who have not heard of Kermit the Frog.