Jam-o'-War

Jellyfish are enemies from Super Mario Galaxy. They appear in the Deep Dark Galaxy and the Bigmouth Galaxy. They are a large, blue variant of Jammyfish. If Mario comes in contact with one, he will be shocked. They can only be defeated by hitting them two times with a Koopa Shell, and will give one Coin when defeated. After they are attacked once, they glow green, but don't act any more aggressively.

In Super Mario Galaxy 2, a Jellyfish appears in the Cosmic Cove Galaxy. It behaves the same way as in the predecessor, but instead of giving a Coin when defeated, it will give ten Star Bits.