The 46-year-old, who is starring in the new Disney flick The Sorcerer's Apprentice, admitted that he indulged in the very un-Disney-like activity when he found out his cat Lewis had got into the fridge and eaten some of his stash.
He told David Letterman: "I had a bag of mushrooms in my refrigerator. My cat used to sneak into the refrigerator and eat them.
"The cat ate them voraciously, so I thought what the heck, I'd better do it with him.
"I remember lying on my bed for hours and Lewis was on the desk across my bed and we just stared at each other for hours - not moving, just staring at each other, and I had no doubt that he was my brother."
Nicolas took care to point out he no longer gets funky with fungus... but the spaced-out expression remains!