Brambleguard Captain

Creature — Mouse Soldier2/3$0.24

At the beginning of combat on your turn, target creature you control gets +X/+0 until end of turn, where X is this creature's power.

Legal in Commander

Is

Commanders whose abilities work with this card and share its colors, from what the cards do.

Mabel, Heir to CragflameBrambleguard Captain is a Mouse, which Mabel, Heir to Cragflame can use.
Commander MustardBrambleguard Captain is a Soldier, which Commander Mustard can use.