From the Super Mario Wiki
The Intergalactic InSinkErator (or In-Sink-Erator) was the industial-sized garbage disposal system of Darth Koopa's Koop Star. It was 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 used a flow chart to explain that the garbage disposal works on different levels. On the top level was a large funnel, leading down to a series of buzzsaws. Below the buzzsaws was an unseen section where garbage was compacted into a Garbage Pod. The section below that was where the Garbage Pod was to be ejected into outer space.
Upon pressing a button, Mouser dropped Mario, Luigi, Princess Toadstool and Toad from the platform that they were standing on down into the top section of the Intergalactic InSinkErator. As Mouser left the area, he failed to notice that Mario used his plunger to get a grip on the funnel above the buzzsaws, while his friends grabbed ahold of him. The Intergalactic InSinkErator reminded Mario and Luigi of the garbage disposals they used to fix back in Brooklyn, which always had silverware stuck in them. This prompted Luigi into jamming the blades by dropping the utensils he had on him into the InSinkErator, allowing Mario's group to safely fall past them.
Although the rest of the Intergalactic InSinkErator remained unseen, Mario's group made it through alive, and ended up packed inside a Garbage Pod, which led them to the Mushroom Colonists' Planet.
The Intergalactic InSinkErator was never seen again, as it was destroyed, along with Koop Star, when Mario blew up the foundation of the spacecraft with a Bob-omb.