From season 9 episode "The Dealership".  The heavy-set mechanic who refuses to give George change for the vending machine.  George put money in the vending machine, but his Twix candy bar got stuck on the way out.  Later, George suspects the mechanic put money in the machine, and got 2 candy bars... including George's.  Quote from George... "Alright, Puddy, listen, and listen good. I need to know the name of that mechanic that walks around here. Big guy, a liar. Short name. Sam? Moe? Sol?!"