Fish Are Funny
Courtesy of David Mankins, a fish joke from Japan:

"Sakanaya no ojisan ga odoro ita."
"Gyo!"
"Nanchatte."

Translated:

"The old fish monger was surprised."
"Gyo!"
"Just kidding."

"Gyo" is the sound that they use for being surprised in manga; it's also a way of reading the character for "fish" in Japanese. Maybe that's why fish always look surprised.