Willie Nelson and Snoop Dogg are mixing work with play in Amsterdam. The country icon and rap superstar recorded a song and video there together on Sunday. And if you're wondering what those two have in common, well Sunday just happened to be April 20 -- "4/20" -- a self-proclaimed holiday for marijuana advocates.

Nelson and Snoop followed their recording session with a surprise performance together Sunday at Amsterdam's Melkweg concert hall. You can see pictures from the show here.

Nelson's granddaugher, Martha, and her two friends are blogging from Amsterdam about the experience. They say Nelson and Snoop have become good friends across the pond, writing that they met the rapper in Nelson's hotel room.

"And there – believe it or not – was the one and only Snoop Dogg with his entourage 'in da house,' playing dominoes with Willie and watching Willie do some pretty incredible card tricks," they write on the blog.

There's no word yet on the title of the Nelson-Snoop duet, though they performed a song called 'Superman' at the live show. This is actually Nelson's second recorded hip-hop collaboration. He sang 'Back on the Road,' an urbanized version of his classic song, 'On the Road Again,' with rapper 'Lil Black almost ten years ago.

This isn't Snoop's first foray into country either. The rapper was a presenter at the CMT Awards earlier this month, where he made a lot of new friends with whom he may be collaborating in the near future.

"I have a new single called 'My Medicine' and I wanted to get a lot of country artists to perform on it," Snoop Dogg told reporters backstage. "It was inspired by country music and the late Johnny Cash."

Snoop is a big fan of the Man in Black. In fact, he sported head-to-toe black at the CMT Awards, "in dedication to my main homeboy, J.C.," he said.