Alle Kinder heißen Rune, außer einer: Fisse.
All the Children
Explanation
Explain Bear
Listen up, buttercup! This here joke is playing on a classic German joke structure. It's like saying, "All the kids are doing X except for one kid who is doing Y." In this case, all the kids are named Rune, but one is named 'Fisse' which is a crude word for vagina in German. Haha! Because saying bad words is funny!