It's called Mike Cover for Wii U. And yes, it really looks like a toilet plunger.

Wii Karaoke U is a service that's been available in Japan for a while, a built-in app for Nintendo's console that lets users play a basic singing game using their Miis. The game - developed by Joysound - went and hit Europe last month, converted to a downloadable title, and the song selection is...interesting.