"You can tune a piano, but you can't tune-a-fish!"
You Can't Tuna Fish is a gag technique used by Tien Shinhan.
This technique is basically a joke that is a play on words, as tune a fish sounds like tuna fish.
It was originally used by Tien Shinhan to make King Kai laugh in order to train under him, Yamcha was the one who told him the joke. As Tien is a stoic person, it was hard for him to make King Kai laugh, so in order to finally deliver a successful joke, Tien must literally power up and use the Multi-Form technique as he aggressively declares "You can tune a piano, but you can't tune a (tuna) fish" in the English dub, and "You think what's up your nose is a secret but it's not (snot)" in the Japanese dub. It succeeds allowing Tien to take part in King Kai's training alongside Yamcha, Chiaotzu, and Piccolo.
Video Game Appearances
You Can't Tuna Fish was named in Dragon Ball Fusions, where it appears as one of the gag-based Special Moves. It has a chance of powering down one enemy. It can be learned by Yamcha after reaching Lv. 30.