Get them in the same room, sit them down on the floor, Indian-style(that's what they say at school, what do you want from me?) back-to-back, and have them lock elbows. Now they have to stand up. It takes teamwork. If that doesn't work, get a big huge long rope, tie them and a few other people together in a giant knot(more people=more fun) and have them work it out. Together. My friends do this all the time.
^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ^_^ ← I LOVE that emoticon. Can you tell? ^_^