We've travel quite a bit around the holidays (though never to Disney.) Here are a few of the less messy/easier ideas we use when in a hotel room.
1. Toilet Papering:
Our elf has toilet papered the headboard, lamps and ceiling fans in hotel rooms. Just go light on the toilet paper so that it is fast and easy to clean up.
2. Dry Erase Markers:
Dry erase markers easily wipe off of mirrors. Our elf has used them to write different sayings on mirrors and to draw a picture of himself on a mirror. When we're ready to leave for the day, we just grab some toilet paper and wipe it away before the maid comes in.
3. Bath in the Sink:
Elf fills up the sink and use the drain stopper to keep water in there. Elf then puts on the shower cap (bring a small rubber band so you can make sure it stays on) and sits beside the sink next to the shampoo and conditioner bottles.
4. Mustaches:
Our elf was caught putting those sticky mustaches on a couple of DSs stuffed animals. 2 already had mustaches on them, and he was standing over the third animal with a mustache in hand. DS thought it was funny that he was caught in the act. Just plan ahead to buy the mustaches, but it is easy to set up and easy to clean up.
5. Elf Bank Robber:
Our elf robbed a bank in the middle of the night. When we woke up, there were wanted posters in our hotel room, and we caught Elf hiding with a bandana over the bottom half of his face, and a sack of gold chocolate coins. I think I remember seeing chocolate coins and dollars in Disney, so this may be very easy to pull off there, if you just print a couple posters before you go.
I think if you're good at Photoshop, you might even be able to take a couple of the Disney ride pictures or Character pictures and insert elf's picture (and maybe even some of their other stuffed animals) into the photo. Have elf sitting around the table looking at his ride/character photos, so it seems like he snuck out and played in the parks all night.
Or, if your kids have autograph books, maybe you can use a page where Elf adds his autograph. Make it special with stickers or something fun and interesting. Then place elf sitting by the books with a pen in his hand.