CBS TV's "How I Met Your Mother" star Neil Patrick Harris says he wasn't the sitcom creators' original choice for the character of Barney.

"They initially wanted a John Belushi, Jack Black -- a big, portly cigar-smoking kind of guy," Harris told Julie Chen on CBS' "The Early Show."

Harris -- whose breakout role was teenage genius "Doogie Howser M.D." from 1989-1993 on ABC -- has received raves for the "Mother" role he wasn't even expected to get.

"I went in (to audition) with no expectations at all," he told Chen. "In pilot season we do lots of auditions and you rarely get anything. I went in and kind of made an ass of myself. And that's what they wanted. I did a dive roll, actually."

As for his womanizing character, Harris said even he has no idea exactly what Barney does for a living, except that it involves the "dark arts."

"We know he's involved in the high up (corporate) darkness ... maybe oil spilling, maybe cigarettes, tobacco lobby," he said.