The Pizza Twins

From Muppet Wiki

Fozzie and Kermit disguise themselves as the Pizza Twins, a pair of identical twin pizza delivery boys, during "The Great Muppet Caper". They bring a pepperoni pizza to the guard of The Mallory Gallery.

In the movie, the two play twin brothers, and the only distinguishable difference between them is that normally only bears wear hats. Because both wear hats as part of the Pizza Twins costume, Fozzie speaks in a ridiculous (and poor) Italian accent to differentiate himself from Kermit, and to help the audience tell the two characters apart.