You can have them have them say "Oh crap." in a calm voice if they get stuck.
If their forces are falling "Uh, can I switch sides?", "No fair!", "What ARE you?"
If it's hiding "If I can't see them, they can't see me."
And just for giggles: "Since when did you guys start winning?" and "No Me GUSTA!!!!"(I don't like in spanish.) "Oh I'm hot!" "Eat IT!!!!"
If you pick any of ours, will you let us know?