F is for friends who do stuff together

@Rokasu F is for fire that burns down the whole town!
U is for uranium!
...bombs.
N IS FOR NO SURVIIIIIIVORS
WHEN YOU-

Plankton! That's not what fun is about!

@BlueMetalChick Now do it like this

@ImRileyTheDog F is for frolic, all through the flowers
U is for ukulele
N is for nose picking, chewing gum and sand-licking
Here with my best buddy

@Elegy It's from an episode of SpongeBob SquarePants called "Fun." The plot involves SpongeBob trying to make friends with the show's main villain, Plankton, by showing him how to have fun instead of being a miserable and vitriolic bad guy all the time. Sponge makes up a song called the "Fun Song" in which he sings lyrics about each letter of the word "Fun" standing for something.

@BlueMetalChick Logical explanation filed and cataloged, thank you BMC.

@BrattyMel hahaha