Ram, 41, said he had so much fun with his female co-star during the filming of the Devang Dholakia-directed movie.
"When we began shooting, I knew I was going to work with this hot, beautiful and in demand actress. But I didn't know we would have so much fun.
"People know I am a big prankster, Sunny is way beyond me. She is a tomboy and it doesn't come across easily. She has no problem if somebody pulls her leg and she will give right back to you. Normally, I have this kind of fun with the guys, but this is the first time with a girl I had so much fun," Ram told reporters here.
"In actors, I have always been obsessed with men because I wanted to be like them. Like Sanjeev Kumar, Robert De Niro, I would watch their work again and again and be obsessed about it, not really the women," Ram, who is married to Gautami Kapoor, said.
"Kuch Kuch Locha Hai" hitting theatres this Friday.