There are so many choices!
1) Break your leg.
2) Claim you have the runs, and can't stay away from toilet for long.
3) You have Tourette's. Be creative, and as foul mouthed as possible.
4) Dance with him. Sexily. Give him 'the look'. While pretending to have a bog eye.
5) Affect a twitch that involves entire limbs.
6) Sneeze/cough without covering your mouth.
7) Have problems controlling the volume of your voice. Whisper, then when he leans in close to hear what you're saying, shout at the top of your lungs.
8) Tell him you'll only dance if he agrees to have a dance with your other hot, single friend. She's called Mary, and lives in your mind...
9) If it's a slow dance, drool on him.
10) Tell him he's the first guy to ask you to dance since your post-op party. Ask if he wants to guess what kind of op it was.
Or... Just tell him you don't dance with creepy guys like him!