From the Super Mario Wiki
A Calm Hammer Bro is an enemy living on Vibe Island, in Super Princess Peach.
Like other Calm enemies, the Calm Hammer Bro spends most of his time asleep. Princess Peach can either walk past or attack him. If the Calm Hammer Bro wakes up, it will attack like a regular Hammer Bro. However, their briskness depends on how long they've been awake: if they have just woken up, they will throw their hammers at a slow rate, while their attack is much faster when they've been awakened for a long while.