I see this happen all the time with my players. I might be describing the environment they're in just to set the scene and they'll focus in on something specific. I'll set what I think is a fairly straightforward goal only for them to come up with an insane hairbrained scheme to accomplish it.

But the greatest one, I think, probably came when I was GMing the Lost Mine of Phandelver for a group of people completely new to roleplaying. We got to a section where they rescued a character they were after from a dungeon he had been trapped in by a doppelganger. I had the doppelganger transform into the trapped character, right in front of their eyes, and make a last-minute plea that he was actually the real prisoner and the other was fake. Claimed he had been transformed by a magical potion that had just conveniently expired at the right time.

I figured this was a last-minute hail mary on the part of the doppelganger, with zero chance of working. They'd immediately reject it and execute or capture the doppelganger and free the real prisoner. Instead, they spent easily half an hour debating which was real, casting spells like zone of truth and painfully agonising over every detail. They got it right in the end, but it was just hilarious to watch them completely overcomplicate what was meant to be a very simple bit of flavour text.