From the Super Mario Wiki, the Mario encyclopedia
The pipe creatures are two giant characters in the TV series The Adventures of Super Mario Bros. 3 where they appear in the episode "A Toadally Magical Adventure". Originally, they were normal pipes, but Toad transforms them into live beings with the Wizard King of the West's wand. At first they are peaceful, as Toad only instructs them to make noises out of their pipe holes, but he keeps bossing them around to make louder and faster noises. This causes them to become angry, so they steal the wand from Toad and bring to life a couple of blocks to terrorize Toad.
King Koopa later comes and sees that the pipe creatures had the wand. King Koopa then instructs some Boomerang Brothers. to get the wand. The pipe creatures dodge the boomerangs with ease and laughed, but are caught off guard when they came back, and they lose the wand. Koopa then freezes them with the wand.
Later, Bully Koopa makes the pipe creatures play a game of catch with the Mario Bros. and Toad as the balls. Cheatsy Koopa makes a giant Nipper Plant attack Mario, but the blue pipe creature is hit instead. Mario then wrenches the purple creature's arm off to free Toad. However, the blue one catches Mario again, and is then destroyed after Mario turns into Raccoon Mario.