If a player asks a question about how something works, and you suddenly realise that it doesn't work, just make something up quickly and pretend that you had it planned that way all along, and that it makes perfect sense that way.

Audacity is the GM's best resource.

Transcript

GM: The next thing on stage is a musical number performed by a group of fish.
Fish 1: {singing} Down in the meadow in a little bitty pool
R2-D2: Sure. That makes more sense than—
C-3PO: How big are the fish?
GM: Smallish. They call in another not so small fish.
Fish 2: Swam three little fishies and a mama fishie too.
R2-D2: Wait. Is the stage flooded then?
GM: Uh, no. They're... suspended by force fields. And they're holding their breaths.
R2-D2: While they're singing?
GM: If you guys can get away with it, so can I!
Fish 3: They swam and they swam, and it was a lark. Till all of a sudden they met a shark!
C-3PO: Let it go, Artoo. We've got bigger fish to fly.