Hobogetarian

A person who eats from other's plates when they finish dining, or consumes other's take-home leftovers from the counter or refrigerator.

"I brought home half a pizza last night and it was gone this morning! I think my roommate is a Hobogetarian."

Or...

"Are you finished with that Crab Louie?"
"Dad, don't go all Hobogetarian on me. Order your own."