McConaughey tells the story to Jimmy Kimmel, explaining how they were shooting a scene together when the "Snooping" occurred.
"There's a scene where I'm going to Snoop because I've got writer's block and Snoop has the magic weed. So I went to the prop man to make sure I have the prop weed which is like crushed oregano," said McConaughey.
"We pass back and forth and all of sudden at the end he goes 'Yo Moondog' [his character], that ain't prop weed, that's Snoop Weed,' and I was like 'Oh you son of a a gun,'" laughed McConaughey.
It was only when they'd finished filming the scene that Snoop revealed the 'prop weed' was actually real.
"The next nine hours were a lot of fun but I don't think we used one word in the English language," said Matt, obviously enjoying being on the receiving end of the joke. "I got Snooped!"
It turns out that McConaughey is a seasoned pot smoker, after infamously being arrested while high in 1999. He was taken into custody by police while reportedly naked and playing the bongos, as the legend goes.
His latest stoner adventure, The Beach Bum, also stars a ripped and interesting looking Zac Efron, and while not much is known about the plot yet, it seems as though making this film might have been just as fun as watching it will be.