A myth that many people used believe in, however it was so mythbusted to the point where the actual truth became common knowledge.
Bill: Hey John did you know tomatoes are actually-
John: Fruits. Dude that myth is long mythfucked.
Bill: John don't chew on that pencil! You'll get lead poisoned.
John: There's no lead in this, dumbass. I'd thought you know since it's been mythfucked.