FutureMovies offers a Q&A interview with Michael Gambon, Harry Potter's current Professor Dumbledore and one of Johnny Depp's co-stars in Sleepy Hollow. In it, he discusses joking around with Johnny:

Your Sleepy Hollow co-star Johnny Depp told us you are a bit of a joker…

Well, he can shout.

Can you tell us about one of your practical jokes?

On my first Potter film, the director and I shoved a fart machine in Harry Potter’s sleeping bag. He had his eye on one of the extra girls and asked, “Can she be in the next sleeping bag to me in this scene?” She was a beautiful girl playing a non-speaking part so we agreed. I had the controller, and as soon as he wakes up in the Great Hall, I pressed the button. It destroyed his credibility with her.

Did you get the idea to use a fart machine from Johnny Depp? He’s used them on sets before, hasn’t he?

Johnny’s constantly using fart machines – but this one wasn’t one of his. I bought this one.

Have you played any gags on Depp?

My best joke on Johnny Depp was when we were filming inside this stately home in England. It’s the only place where the Queen can ride her horse from Windsor without going on public roads.

What happened?

Well, the Queen came past one day – and everyone was gobsmacked. She obviously had her entourage, but next to her was a friend of mine called Henry Herbert. He was the 17th Earl Of Pembroke, and he’s also a film director. As they went past, I’m standing there with all the actors and Henry shouts, “Hello Mike.” So I reply: “Hello Henry, how are you mate?” The Queen waves like she was talking to me and on they went, but Johnny was speechless. He asked: “Do you know her?” And I said: “Yeah, she’s a mate of mine.”

And he believed that?

Well, he did because it was such serendipity. You couldn’t want for a better fake. I said to him, “I’m always nipping in her house for a cup of tea.”