Finn's favorite fish's favorite food fell flat.
Finn's favorite fish's favorite food falls for fluid.
Finn's favorite fish's favorite food fed Finn's favorite fish.
Finn's favorite fish falls for Finn's favorite fish's favorite food.
Finn's favorite fish's favorite food falls for Finn's favorite fish.
Finn's favorite fish's favorite food fills Finn's favorite fish.
Finn fishes for Finn's favorite fish's favorite fish food for Finn's favorite fish!

Rebecca Ryan

http://www.poemhunter.com/poem/finn-s-favorite-fish-long-tongue-twister/