Updated

Texas Gov. Rick Perry, after offering up late-night fodder with his forgetful moment at this week's Republican presidential debate, opted to get in on the joke with an appearance on David Letterman's show Thursday night.

Capping a day of interviews in which he tried to laugh off the embarrassing moment, Perry gave the TV audience his own list of "Top 10 Rick Perry Excuses" for being unable to remember which three federal agencies he would eliminate.

In a separate interview on Fox News Thursday night, Perry explained that the campaign decided to have a "little bit of fun with it." His campaign website invited people to comment on which agency they'd like to forget -- Perry said the site got over 2,000 hits Thursday.

On Letterman, Perry chalked his brain freeze up to everything from Mitt Romney's good looks to a deficiency of energy drinks.

"Hey, listen. You try concentrating with Mitt Romney smiling at you. That is one handsome dude," Perry chuckled during his segment with the comedian.

At the debate, Perry could only come up with the names of two of the three agencies he had promised to get rid of if elected president, ending with a grinning, "Oops."

Perry later said he would eliminate the Commerce, Education and Energy departments.

He also acknowledged that he had "stepped in it" during the debate.

The Texas governor is trying to turn the stumble into an opportunity. He is asking supporters to pitch in a few dollars for every agency they would abolish.

Perry's Top 10 excuses on Letterman:

10. "Actually there were three reasons I messed up last night. One was the nerves, two was the headache and three was, and three, uh, uh. Oops."

9. "I don't know what you're talking about. I think things went well."

8. "Hey, I was up late last night watching `Dancing With the Stars."'

7. "I thought the debate was tonight."

6. "Hey, listen. You try concentrating with Mitt Romney smiling at you. That is one handsome dude."

5. "Uh, el nino?"

4. "I had a five-hour energy drink six hours before the debate."

3. "I really hoped to get on my favorite talk show, but instead I ended up here."

2. "Hey, I wanted to help take the heat off my buddy Herman Cain."

1. "I just learned Justin Bieber is my father."

The Associated Press contributed to this report.