It might add too much complexity, but Paragon Avenger had a good thought:
And how about giant christmas presents, either non-clickable or when you click them they reponse kind of like the doors do.
"This package isn't for you."
"Hey, not until Christmas."
"Snowman local 315 on strike"
"Did you see your name on this, go buzz off."
"You peek inside, it's socks and underwear. You re-wrap the present."
"This package brought to you by NCSoft. Have a whole lot of nothing." (ok, maybe not this one.)
Mix those in with the 'working gifts' as a parody of the Paragon Chat door setup?
Some more ideas:
"Thin Mints. Just like the last five presents."
"Cordial Cherries. Just like the last five presents."
"It's Fruitcake. People still make these on purpose?"
"You found a DVD... of your best friend's vacation photos from last year set to 1980's music. Fun, I guess?" (Actually happened to me.)
"Someone gave you a Self-Help Book. Is someone trying to tell you something? Guess not, it's supposedly from 'Santa'."
"Just what you always wanted: A box of Nasal Tissues."
"The philosopher in you considers for a moment: Are you opening the present, or is the present really opening you?"
"The unnecessarily large present has nothing but packaging peanuts from top to bottom. Coal would be more practical..."
"Nah, you can't have this one. You'll shoot your eye out, kid." (A Christmas Story)
"After the paper is removed, it's a cardboard box with the word 'TRANSMOGRIFIER' on it and all sorts of buttons and panels drawn in marker." (Calvin and Hobbes)
"Good news? It's a puppy! Bad news? He's high strung and tearing up all of your other gifts out of boredom."
"Good news? It's a kitten! Bad news? She keeps trying to scale the Christmas Tree and flinging ornaments off wherever possible."
"You opened a present with one slipper in it. Keep looking! The other one has to be out here somewhere..." (Actually happened to me.)
"A bottle of Dish Soap. But it's from a 5-year-old kid who is grinning from ear to ear. How can you say no to that?"
"It's a gift card! But it's for a restaurant chain that's no longer in business."
"You found a dish towel. Embroidered on the towel is a calendar for November 1982. Easiest way to put it? You're confused."
"Remember those Gift Enhancements? It's one of those, except when you activate it nothing happens and another one appears, then when you activate that one nothing happens again and you get another one, and so on and so on..."
"It's a secret encoder ring. The message from the Radio translates as follows: B E S U R E T O D R I N K Y O U R E N R I C H E. What?" (A Christmas Story)
"It's a flash light and a tire gauge... and you don't own a car."
"It's a Paragon Transit Authority Bus Pass good for six months! Come to think of it, when have you ever seen a bus in Paragon City?"
"It's one of those nifty dimension boxes that lead you to a parallel universe... that looks an awful lot like this one. In fact, when you enter it there's no bottom. You realize too late that you just emerged from an empty box in the current universe." (Futurama gag that might be too long for a dialog box.)