Q: If someone plays Trade Hands with me, and I have some Surprises (other than Stop That, which could prevent the trade) can I use them even though they’re not canceling a card play, just so I don’t have to give them to the other player?

A: No. Surprises can only be played for an out-of-turn effect when there is an effect to be had. You can’t just play a Surprise for no effect just to burn it.

When used for their in-turn effect, of course, they behave much the same way as Actions, and, as such, may or may not have an effect.