In Junkyard Tussle, right before entering the room to fight Noiman Cascade, if the player climbs up the wall, they will find a mysterious character who will ask if they want to fight in the battle arena. If the player agrees, they will enter a crowded fighting arena where they will fight Simondo Belmont, Psycho Mother, and the Warp Bomber.
The Psycho Mother is a large ghoulish creature pushing an armored baby carriage featuring a mobile cannon. She fights by ramming the carriage against the wall and blasting the player with missiles. Her equally gigantic and ghoulish child also rises from the carriage and attacks by extending its arms in order to grab the player. Once the child and weapons are taken care of, the mother will keep on ramming the carriage into the wall.
If the player is skilled enough, they can go to a safe zone on the wall and just keep blasting until this boss is defeated.