Time Travel Tube
From the Super Mario Wiki
The Time Travel Tube (or just simply Time Tube) is a time machine that appeared in The Adventures of Super Mario Bros. 3 episode "Toddler Terrors of Time Travel". It was built by Kooky von Koopa in order to allow travel to the past and prevent the Mario brothers from finding their way into the Mushroom Kingdom, allowing Bowser to take over without hindrance. In addition to traveling through time, it is capable of manipulating a person's age.
However, the Time Travel Tube malfunctioned during its journey to the past, causing Mario, Luigi, Toad, and the Koopas to rejuvenate back into infancy. When the Mario brothers and Toad escaped in their baby forms, Kooky repaired the Time Travel Tube and restored himself and Bowser to their proper ages so they can carry out their plans. Before they had succeeded in preventing the Mario brothers' arrival, Toad stole the Time Travel Tube and then restored himself and the Mario brothers back into adulthood. The Mario brothers were able to open and enter the gate into the Mushroom Kingdom before the timeline became permanent, thwarting Bowser and Kooky's plans.