Simon Cowell's heart is apparently warmer than one would expect.

The American Idol judge appeared as a guest during Monday's broadcast of The Oprah Winfrey Show and cut a $162,000 personal check to Amy and Randy Stoen, whose 3-year-old daughter Madeline was recently diagnosed with a rare and aggressive form of cancer.

"I didn't know what to do in this situation other than to do something which I hope will help," said Cowell after making the donation.  "It doesn't stop there.  If there's any problem, I'm her guardian angel now."

In January, doctors in the Stoen's small Minnesota community referred Madeline to the Mayo Clinic after they noticed a cyst inside her nose.  She was subsequently diagnosed with alveolar rhabdomyosarcoma -- a rare and aggressive form of cancer that had spread to the left side of her face.  In an attempt to save her life, doctors immediately began chemotherapy.

"It's hard because I can't do anything for her to take that pain away," said Amy. "She's going to have to do this for a year, and it's going to be a long year."

In order for Madeline to receive the treatments, her parents drive more than 100 miles a day to Saint Mary's Hospital in Rochester, MN, creating a financial hardship for the family.

"The house payment is sitting there and the medical bills on top of that," said Amy. "We're only three weeks into it. We have 41 weeks to go... My job covers the insurance, and his paycheck covers the mortgage. We want at least one parent here, so that means we only have one paycheck coming in versus two."

Since their "main priority" is getting Madeline the medical help she needs, Cowell wrote the person check to ensure the 3-year-old remained the family's top priority.

"I know that you're having trouble with your mortgage. And as of this afternoon, [it] is being paid off," Cowell told Randy and Amy.

Cowell joked his generosity -- which normally includes aiding canines -- is something he only recently discovered.

"I never knew that doing good could feel so good," he said.  "I didn't realize that. It's taken me 48 years.  It's going to catch on, this, because it is a very, very good feeling."