Chris O'Donnell has revealed he loves to play practical jokes on his NCIS: Los Angeles co-star LL Cool J.

The 43-year-old actor stars alongside LL Cool J in the crime investigation series and says they have a great relationship on and off the set.

Speaking to O'Donnell said: "We have a great relationship, he refers to me as having a lot of plausible BS in a nice way because I like to make things up that kind of sound like they could be true, and then he can’t tell if I am screwing with him or not. But we have a good time. 

"I have had a few good practical jokes on him.

"One time I was coming out on the cover of a health magazine and I knew he was going to give me a hard time so I decided to go on the attack before he could do that. 

"So on April's Fools Day I had the prop guys make a fake ad for a protein powder on the inside cover of the magazine I was in – featuring LL Cool J, endorsed by him, and I was like 'O that’s cool you are in here too,' and he was on the phone with his lawyers and I said 'you didn't get paid for that?' and he said 'I'm going to get paid!'."