U.S. President Barack Obama took a short spin with comedian Jerry Seinfeld for his "Comedians in Cars Getting Coffee" web series and told him that "a pretty sizable percentage" of world leaders may be crazy.

In his latest pop culture venture, Obama filmed a special guest spot for the series, streamed on Crackle. Each 20-minute episode features Seinfeld chatting informally with a different comedian.

Obama has "gotten off just enough funny lines to get on this show," Seinfeld said in the episode that hit the web late on Wednesday.

The former star of the hit TV comedy series "Seinfeld" chose a silver blue 1963 Corvette Stingray for the ride with Obama, although for security reasons the pair had to be content with a few slow turns around the White House grounds and the coffee was drunk in a staff dining room.

Amid the small talk, viewers learned that Obama blows off steam by cursing, that his underwear is all one brand and one color, that he shaves before he works out and that his guilty food pleasure is nachos.

"How many world leaders, you think, are just completely out of their mind?" Seinfeld asked Obama at one point.

"A pretty sizable percentage," Obama replied.

"Some of these people, you must meet them, you'll just be chatting and you look in the eyes and go, 'Oh, this guy's gone,'" Seinfeld said.

"Part of what happens is, these guys, I think the longer they stay in office, the more likely that is to happen," Obama said.

Seinfeld and Obama also talked about the drawbacks of fame versus anonymity, how to deal with hecklers, and Obama's most embarrassing presidential moment. "This may be it," quipped the president.

The show follows Obama's appearance earlier in December on the survival adventure TV series "Running Wild with Bear Grylls" in Alaska to highlight the dangers of global warming, his 2014 spoof interview for online video series "Funny or Die" to promote Obamacare and numerous appearances on TV chat shows while in office, including "The Tonight Show," "The Daily Show" and "The View."