NCIS Michael Weatherly Etonline interview

The subject matter on "NCIS" is always totally serious, as the hit CBS series mainly focuses on the solving of major crimes. But little by little, executive producer/creator DON BELLISARIO is introducing info on the personal lives of the characters, and that is a big draw for the fans.

This season for example, Special Agent Tony DiNozzo (MICHAEL WEATHERLY) has a girlfriend, something that hasn't happened to him before, and the former "Dark Angel" star sees it as a sign of growth for his character.

"It is good, because he has the attention span of a gnat," Michael tells ET. "He is like a goldfish that swims from one end of the bowl to the other, turns around and goes, 'Look at this.' It is always a brand new goldfish bowl [for Tony]. I love that about him. He is very enthusiastic. But it means every relationship lasts about three weeks."

While Michael definitely has a longer attention span than his character, the two do share a sense of humor. While talking to reporters during a recent set visit, he admitted that he didn't wear underwear the first two seasons. It was hard to know if he was serious or not.

"I wanted to make sure it wasn't a boring job," he explains. "I didn't want to walk around and say my lines in this monotone. I just wanted to see if I could explode some of the dyed-in-the-wool expectations and the cornerstones of the cop drama. I thought it would be fun, so I didn't wear underwear the first few seasons. You move differently. There was mooning. But when you are a guy and you wear a suit, you don't go commando."

The 38-year-old actor also admits to using cheat sheets to help him remember his lines, whenever there is something complicated or a difficult name. He has been known to tape them to overhead beams, the floor and, of course, on objects on his desk.

Getting to know the "NCIS" cast of characters has introduced audiences to their quirkiness, but it look Weatherly a long time to get his sister to become a fan.

"My sister wouldn't watch it for the first two years, because she was, 'The Navy? Do you have to wear a uniform?' I was, 'Watch the show and then tell me what you think.' She was, 'I promise.' Three months later, I was, 'What do you think?' Now she is, 'Your show is like 'M*A*S*H' with Klinger and Radar. Your show is weird.' I am, 'Yeah.'"

"NCIS" airs Tuesday nights at 8 p.m. on CBS -- where it is doing great against the FOX powerhouse "American Idol."