From the Super Mario Wiki
The Monster Mixer is an invention created by Iggy Koopa for Bowser in Monster Mix-Up. It is an oddly-shaped plane with two beaters on the nose. The Monster Mixer fuses several objects or creatures together to create a single entity. Its effects are strong enough to be felt by everyone in the same room as it, even if they are not the targets.
Creatures created by the Monster Mixer include: