In Gen 3, there is a Hiker in the near the Mauville-side entrance to Firey Path. Before you fight him, he says "Hahahaha!" Immediately after beating him, he says "Something flew up my nose! Hahaha-hachoo!"
On my first playthrough of the game, I was incredibly sleep-deprived and caffeine-high, so this line was incredibly funny. Whenever I remember it, I have flashbacks of spraying Dr. Pepper everywhere.
EDIT: Also, the female swimmer who don't know where to put her Poke Balls.