From the Super Mario Wiki, the Mario encyclopedia
The Intergalactic InSinkErator (or In-Sink-Erator) was the industial-sized garbage disposal system of Darth Koopa's Koop Star. It is only ever seen in The Super Mario Bros. Super Show! episode "Star Koopa."
When Mario, Luigi, Princess Toadstool and Toad are taken prisoner aboard Koop Star, Darth Koopa fails to make Princess Toadstool agree to surrender the Mushroom Colonists' Planet over to him. As consequence, Mouser was ordered to drop the four heroes into the Intergalactic InSinkErator.
Before dropping Mario's group in the InSinkErator, Mouser uses a flow chart to explain that the garbage disposal works on different levels. On the top level is a large funnel, leading down to a series of buzzsaws. Below the buzzsaws is an unseen section where garbage is compacted into a Garbage Pod. The section below that is where the Garbage Pod is to be ejected into outer space.
Upon pressing a button, Mouser drops Mario, Luigi, Princess Toadstool and Toad from the platform that they are standing on down into the top section of the Intergalactic InSinkErator. As Mouser leaves the area, he fails to notice that Mario uses his plunger to get a grip on the funnel above the buzzsaws, while his friends grabbed ahold of him. The Intergalactic InSinkErator reminds Mario and Luigi of the garbage disposals they used to fix back in Brooklyn, which always had silverware stuck in them. This prompts Luigi into jamming the blades by dropping the utensils he has on him into the InSinkErator, allowing Mario's group to safely fall past them.
Although the rest of the Intergalactic InSinkErator remains unseen, Mario's group makes it through alive, and ends up packed inside a Garbage Pod, which leads them to the Mushroom Colonists' Planet.
The Intergalactic InSinkErator is never seen again, as it is destroyed, along with Koop Star, when Mario blows up the foundation of the spacecraft with a Bob-Omb.