George Clooney has "never been prouder" than he is of his prankster son

Amal told 'Entertainment Tonight': "It's really bad because my son has access to Hollywood grade props, like fake cockroaches and mice, and he now has a 3D printer.

"So I can't tell you the things I am finding under my documents under my pillow.

"And when Alexander ex ecutes the pranks and George sees it he just looks at him and he's like, 'Son, I am so proud of you.'"

George confirmed: "Never been prouder".

However, the 63-year-old star - who is also father to Alexander's twin sister Ella - admitted he's also often subjected to his son's jokes.

He said: "Now he'll call me and he's like, 'There's something important I have to tell you Papa,' and I'll go, 'What?' and then he hangs up on me."

Amal quipped: "He's learning from the best."

The 'Midnight Sky' actor recently spoke of one of his own favourite pranks, using stationery with Brad Pitt's header to fool fellow Hollywood stars with "brutal" letters.

One was sent to his friend's 'Interview with a Vampire' co-star Tom Cruise suggesting they make a sequel to their 1994 movie - but that they swap roles.

George told talk show host Jimmy Kimmel: "I sent it to Tom Cruise, saying they want to do ['Interview with the Vampire 2'], but this time Brad wants to play Lestat."

Jimmy laughed: "Brad this afternoon said that Tom called him and said, 'Yeah, it's cool, you can play Lestat, that's fine, I'm OK with that,' and he was like, 'What are you talking about?'"

And when it came to Meryl Streep, the former 'E.R.' star sent her a gift that 'Brad' felt would come in useful for her.

He explained: "I sent [a letter] to Meryl Streep with a box of CDs for dialect and I said, 'This guy helped me with my accent in 'Troy' and I think it could really help you.' "