It is also a tongue twister that Danes use to mercilessly screw with non-Danes. They'll make you say it. If you're not from Denmark, it's impossible. They will laugh. Hard.
Person A: Dude, my friend makes the best rødgrød med fløde ever, and she’s not even from Denmark!
Person B: The fuck did you just say bruh?
Dane: Can you say rødgrød med fløde?
Non-Dane: Ro, gro, meh flu?
Dane: Haha, dumbass.