IJ -
Lock ball without hitting any drop targets "You cheat Dr. Jones"
Cairo Swordsman, pull trigger to shoot him instead of hitting mode start.
Shadow -
Pull trigger when ball is in one of the saucers for "Anyone for Peking Duck". Do this for all 3 and you get "Secret Laugh Mode" as your next mission.
MB -
This is a tough one to do, but is super funny if you can pull it off.
Failed right ramp shot that comes back down and hits Dracula in his backside makes him say something like "That's my ass".