David Letterman is absolutely fascinated by how the kids these days are smoking marijuana. Luckily for him, unofficial Ambassador of Cannabis Seth Rogen was his "Late Show" guest on Wednesday, and Rogen indulged Dave's curiosity about thenow-kind-of-legal drug.

"Say that you and I go into the weed store, and I say, 'Seth and I would like a joint,'" Dave asked the "Guilt Trip" star. Letterman was panicked that weed today is much stronger than it was when he smoked it in the '70s with Robin Williams, when the only discernable side effect was that users would feel like taking a nap.

He was also astounded that young people can multitask while smoking pot. "You can actually play video games with that kind of fog in your brain?"

Rogen grinned. "I think that my generation is very accustomed to being stoned and playing video games," he said to much laughter and applause.

"The future of America, ladies and gentlemen," Dave quipped.

Check out the video above, where Rogen also admits that he couldn't get his co-star Barbra Streisand to toke up with him, and that Rogen's hometown of Vancouver, British Columbia has the most "primo" bud.