Kat Dennings revealed that Josh Groban once wrote her a "ridiculous" song called "Steam Cleaner Lady"
Credit: Michael Rozman/Warner Bros.

Kat Dennings thinks boyfriend Josh Groban is a genius.

In a Thursday appearance on The Ellen DeGeneres Show, Dennings can’t help but sing her man’s praises.

“Obviously you know how talented and amazing [Groban] is,” the 29-year-old tells host Ellen DeGeneres. “But what you may not know is that he’s one of those people who can sit at a piano and play anything, anything off the top of his [head] he’s just, he’s just a genius.”

The 2 Broke Girls star even gushes about the “ridiculous songs” she and Groban make up together.

“Once I was steam cleaning the floor – because I like to steam clean,” Dennings begins. “And he sat down at the piano and made up a song called ‘Steam Cleaner Lady.’ ”

Naturally, DeGeneres inquires why Dennings was steam cleaning the floor.

“Because we had a party for his birthday and someone spilled honey on the floor – it was a real rager,” Dennings responds.

Groban, 34, and Dennings began dating in October 2014 after being introduced by Dennings’s 2 Broke Girls costar Beth Behrs.

Behrs previously told PEOPLE that the two are “nerds at heart.”

“They’re in this crazy business, they’re both very calm and mellow and wonderful,” Behrs said. “And he treats her like a princess, and it’s amazing.”