Beam Me Up, Scotty!: In-universe; in a realistic touch, Joe quotes The Godfather off-hand to Kathleen, but misquotes it as "I didn't know who you were with." It's actually "You should've told me your boss was Corleone."
Playing Against Type: Steve Zahn and Dave Chappelle play low-key comic relief as opposed to their more over-the-top roles.
Throw It In: When Tom Hanks accidentally closed the door on the string of the balloon leaving The Shop Around The Corner, he popped it open for a moment to free the balloon and added the line, "Good thing it wasn't the fish!"