Requesting to see mucked cards at showdown?

[Dagger78]

I was wondering if there is any type of rule about this, or is it cardroom specific? The reason I ask is because this rule is in place to pervent collusion(please correct me if I'm wrong), and I've been asked to show my cards in heads up pots from people not involved in the hand. Nothing really irritates me at the poker table except when some guy asks to see my hand just because he wants to know what I played that way. I'd really rather not share how I play if I can avoid it.

Should I just ask a floorman when I arrive on the house's specific rules concerning this?