Being good friends with the Characters, just don't be afraid to ask them to do a crazy pose. They love it when guests want to do something different, especially since 99% of the time people just come up, put their arms around the characters and smile. You can do the back to back with the arms crossed, bevel with Minnie, Hold up a "Number 1" finger with Donald, Crouch down with Pluto or whatever else you can think of

Just remember though, that if you'd like to touch the character's heads or anything, just make sure it's okay with them first. For example, "Hey Pluto, is it okay if I hold up your ear?" or something along those lines.