Clear Pipe Cannon
From the Super Mario Wiki
Clear Pipe Cannons are a type of cannon appearing in Super Mario 3D World and later in Captain Toad: Treasure Tracker. As the name suggests, they appear on the ends of certain Clear Pipes, and are used to launch players to new sections of a level. In Super Mario 3D World, like with Warp Pipes or Warp Boxes, if one player enters a Clear Pipe Cannon, all other players that don't enter are automatically drawn into it soon after. Clear Pipe Cannons at the start of a Clear Pipe automatically launch players, while the cannons on the end must be fired manually.