Here's one of my favourites:
"Fluttershy's not a tree!"
"I know..."
"Hey Twilight, Rainbow Dash thinks Fluttershy's a tree!"
"Wait, did you say that Fluttershy's a tree?".
"Yes, but..."
"You do realise Fluttershy's not a tree, don't you?
"I'd like to be a tree."