I broke a player's brain in college playing DND where an NPC just lied to her.

She'd asked where so-and-so was. NPC didn't like her or her faction, so he just lied and said he'd taken up boxing. This isn't an especially credible lie because so-and-so was a lightweight nerd. But she says okay and goes tearing up the local boxing clubs, and can't find the guy.

She's like "where is he?"

Me: "you don't see him, and no one's even heard of him."

Her: "but the guy said he was here"

Me: "he did"

Her: "so where is he"

Me: "doesn't look like he's here"

Her: "but he said he was"

Me: "he did say that"

Her: "so why isn't he here?"

This went on for a while until one of the other players got impatient and said "the guy who doesn't like you maybe lied to you! Or was wrong! Can we move on please??"