Tina Fey is Kermit.
The guy with the hat is Animal.
Jenna is Miss Piggy.
Tracy is Fozzie.
Kenneth is Scooter.
After that the pattern breaks down a little. Jack Donaghy is the biggest exception, a hybrid of Scooter's old man and the two old guys in the back who make fun of the show. The bald guy is a hybrid of Rolf and Scooter.