From the Super Mario Wiki
Chows are stronger variants of K-9s that appear in Super Mario RPG: Legend of the Seven Stars in Land's End. They have no weaknesses, although they are the more basic enemies in Land's End. Chows claim to have already fought Mario, as shown by their Psychopath thought, which suggest that these are upgraded versions of the same K-9s Mario fought previously.
Chows, as their weaker K-9 versions, can Howl to generate the fear status effect on one of Mario's party member, halving his or her attack and defense. Similar to the K-9s' Fang, Chows can use Claw, which deal twice as much damage as a normal move. Unlike K-9s, however, Chows can use poison on one party member.
A Chow also appears as a friendly non-playable character in Monstro Town where he will give Mario a prize based on how many consecutive Super Jumps he can do, the prizes being Attack Scarf for thirty and the Super Suit for one-hundred.
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