From the Super Mario Wiki
The Hammer Bro. Captain
trying to help Peach escape.
“Johnson! I am your captain! Now drop and give me twenty!”
—Hammer Bro. Captain, Super Paper Mario
The Hammer Bro. Captain is a minor character in Super Paper Mario. When Princess Peach awakens in Castle Bleck, after her false wedding to Bowser, the Hammer Bro. Captain and Private Koopa, another member of the Koopa Troop, appear. The Captain orders Private Koopa to escort Peach out of the castle. He runs ahead to try and hold off the brainwashed Koopa Troop members, but instead gets brainwashed himself by Nastasia, which turns his pupils red, unlike other Hammer Bros. encountered in Castle Bleck. When Peach and the Koopa find themselves at a dead end, the captain is seen among the soldiers that arrive with Nastasia. He is not seen anywhere else in the game, and it is unknown what happened to him after the game's events.