From the Super Mario Wiki
The Pinball is an object that appears in the Game Boy Advance game Wario Land 4. The Pinball only appears in the level Pinball Zone, which is the fourth level of the Ruby Passage. Pinballs have faces on them that resemble those of Chain Chomps, with teeth, eyes, and red, blushing cheeks. Four of them appear in every room that holds a Pinball area, and they are used for throwing in little slots to destroy the Pinball Block that guards the door to the next room. For each Pinball correctly placed, the digital-like number on the Pinball Block will decrease by one. When all Pinballs are thrown into the slots, the Block will read zero. The number will flash rapidly, then the Pinball Block will disappear, dropping a 500 Coin, and the door will become accessible, leaving Wario to procceed to the next room.