"It's not always that Democrats win" the poll, she said. "It's not that we're some left-wing show and that's the only kids that watch us."
Nickelodeon has been in touch with Romney's representatives since April and they had been "encouraging" about prospects for the former Massachusetts governor's involvement, Ellerbee said.
The candidate has until Monday to reverse his decision, she said.
An Obama campaign spokesman jumped on Romney's decision when asked for comment, saying, "It's no surprise Romney decided to play hooky" and jabbing at the GOP candidate over education and PBS funding.
"Unfortunately for Mitt Romney, 'The dog ate my homework' just doesn't cut it when you're running for president," spokesman Adam Fetcher said in a statement.
For the special, Obama fielded questions regarding gun control, jobs, illegal immigration, same-sex marriage and bullying. He also was asked about his most embarrassing moment, Nickelodeon said.
"Running into the wall is par for the course for me," the president replied. "I'm running into doors and desks all the time."