Jonah Hill researches his movies by making prank calls.
The 32-year-old actor used to make and record joke phone conversations when he was in college, and admitted he still makes spoof calls today in an effort to develop his characters without people realising his true identity.
He admitted: "What's interesting is that I still do it now all the time.
"I do it to get into character. I'm now recognisable in some ways, so I can't really try out a character in real life, [and] the closest version of trying out a character in real life is playing a version of it over the phone.
"Customer service is the best because they talk to you with real patience.
"I'll just ask about different products, and complain about different products in the way that I think the character would complain about those products."
But Jonah insists he feels "bad" for the other person on the line and will always "buy something" at the end of the call.
He said: "I usually buy something at the end. I feel bad."
In The Wolf of Wall Street, Jonah had to don prosthetic teeth to play Donnie Azoff, and the mouthpiece changed the way he spoke, adding a distinct lisp, and he admitted making prank calls helped him find the right voice for his character.
Speaking to David Remnick at the New Yorker Festival, he said: "I had to learn how to re-talk with them, and then it helped it just sound like this very specific way of speaking, which I really liked, and which we ended up using.
"I don't have many props, but I still have those teeth."
David joked: "You can use them to call Best Buy."
Jonah replied: "I did! That's how I got used to talking with them on."
- Bang! Showbiz