Alright....a few more ideas...
American Pie (Don McLean)- The Electric Mayhem (with Floyd on lead vocals). Unfortunately, Sam the Eagle steps into the numbers, misunderstanding the song. (In a sorta situation to "Mack The Knife")
Don't Stop Believing (Journey)- starting off with Kermit and Miss Piggy, but soon are joined by everyone.
Hurts So Good (John Cougar)- Gonzo, trying out a rockstar makeover. The electric guitar he tried out then explodes on him in the end.
Footloose (Kenny Loggins)- Scooter, trying to be a bad boy, backed up whatnot bad girls.
I Wanna Dance With Somebody (Whitney Houston)- Annie Sue or (maybe) Miss Piggy, in a Cinderella-esque situation (or something similar to the setting to "Stayin' Alive"). The "Prince" either one dances with could be either Link Hogthrob or a random pig.
9 to 5 (Dolly Parton)- Miss Piggy, Janice, Skeeter, and other female characters/ whatnots as they check in to and get ready for the show one evening.
Something Stupid (Frank and Nancy Sinatra)- Kermit and Miss Piggy (This would be a GREAT duet for them, in my opinion)
Good Vibrations (The Beach Boys)- Kermit, Gonzo, Fozzie, Scooter, Rizzo, Floyd, Beaker, and Animal (In acapella, similar to the Wilson Phillips version of the song)
Wouldn't It Be Nice (The Beach Boys)- (in a flashback) a teenage Miss Piggy, persuading teenage Kermit to fall in love and marry her.
Lollipop (The Chordettes)- Three lollipops (a grape flavored, a cherry flavored and a lemon flavored), and a candy-loving whatnot (whom eats the lollipops at the end of the song)
Lay All Your Love On Me (ABBA)- Miss Piggy, singing to Kermit (and karate chopping a few women out of the way) OR Floyd and Janice, flirting with each other (similar to the version in "Mamma Mia")