Looks like the Joker is up to his old tricks again. In this scene from "The Dark Knight" (at the 44:55 mark), Gordon (Gary Oldman) rushes to the office of Commissioner Loeb (Colin McFarlane) because he believes Loeb will be target of a Joker-orchestrated hit. Turns out Gordon is a little late and discovers that Loeb is about to fall victim to the Joker's sick prank.
The Joker had poisoned the trusty bottle of Clyburn 15 Year Old which the commissioner keeps in his desk drawer. One sip and Loeb is out of commission...get it?...commission? Sorry.
Loeb and Gordon aren't the only ones being pranked in this scene. We the audience are the butt of a joke too. Can you guess what that joke is?