A white flag is an internationally recognized sign of truce or ceasefire, and request for negotiation. It is also used to symbolize surrender, since it is often the weaker party which requests negotiation.
In The Muppet Show episode 221, when Animal took up alligator wrestling as a hobby, one alligator can be seen escaping with a white flag of surrender clenched in its mouth.
Soldiers from warring factions ask "Why Can't We Be Friends?" raising their white flags after Statler and Waldorf fire at them with a gattling gun in The Muppet Show episode 401
The pigs wave flags to surrender during the "Macho Man" musical number in The Muppet Show episode 405
Statler and Waldorf wave a flag of surrender when a member of The Teeterini Family comes flying into their box in The Muppet Show episode 512
Dogs during "The Cat Came Back" musical number in The Muppet Show episode 523
In The Muppets at Walt Disney World, a stuntman in the Indiana Jones Stunt Spectacular waves a white flag of truce after being shot at by Kermit the Frog.
At the conclusion of Muppet*Vision 3D, when the smoke from the cannon fire clears, Statler and Waldorf are crouching in their box, holding white flags and saying "We surrender! We surrender!"