Beef and Cheese Santa
A Santa Claus impersonator who is obviously a fake.

This term was coined in the Will Ferrell's 2003 movie Elf, when he confronts the fake Santa at Gimbel's:

Buddy: You smell like beef and cheese, you don't smell like Santa.
I wanted my child to take a picture with Santa, but the one at the mall is a total Beef and Cheese Santa, so we didn't go.