Blue Pipe

A Blue Pipe is a reoccuring object that appears throughout the Mario series. They first appear in Super Mario Bros.

Paper Mario series
Blue Pipes first appear in Paper Mario of the Paper Mario series where they can be found in Toad Town Tunnels. The first set of Blue Pipes can be accessed after getting the Super Hammer after Chapter 2. The first three Blue Pipes lead to Goomba Village, Koopa Village, and Dry Dry Outpost. However, Mario must fight a Blooper before unlocking the Blue Pipes. The next Blue Pipe can be accessed in the lower floors of Toad Town Tunnels. Mario will then need the Super Boots from Chapter 3 to get there. This one leads to Boo's Mansion. Finally, the last Blue Pipe leads to Lavalava Island and requires a Super Blooper fight to access it. Also, Sushie must be in Mario's party to get to it. This Blue Pipe leads to Lavalava Island.