For years April 1st has been associated with April Fools’ Day and the friendly pranks that go along with the annual holiday. Beginning in the 1960s, friendly pranking became synonymous with the psychedelic hippie collective known as The Merry Pranksters.

Based in California and Oregon properties owned by Ken Kesey – the author of One Flew Over The Cuckoo’s Nest and other novels – The Merry Pranksters’ notorious 1964 cross-country journey sharing LSD in their rainbow-colored bus Further (originally misspelled “Furthur”) established them as vibrant enthusiasts of the psychedelic drug. In late-1965 Kesey and The Pranksters tapped The Warlocks – who changed their name to Grateful Dead – to perform at the first Acid Test in Soquel, California at the house of Prankster Ken Babbs. Over the next year, the Acid Tests proved integral in the improvisational development of the Dead who by that time were the events’ house band.

Along with Kesey and Babbs, other well-known Pranksters include primary Futhur driver Neal Cassady (“Cowboy Neal” referenced by Bob Weir in “The Other One” and the inspiration for the Dean Moriarty character in Jack Kerouac’s On The Road), Carolyn “Mountain Girl” Adams, George Walker, Stewart Brand, Roy Sebern, Wavy Gravy, Paul Foster and others.

Here’s an animated interview with Grateful Dead guitarist Jerry Garcia talking about Kesey and The Merry Pranksters and how the Acid Test gigs came about:

Here’s a slightly less coherent clip of Cassady appearing on KGO-TV ahead of the Acid Test Graduation at the Winterland Ballroom in San Francisco on October 31, 1966:

Cassady makes a cameo in this video montage of scenes from a 1966 Acid Test Graduation (with music from a 1968 Dead show):

For a complete look at Kesey and The Merry Pranksters, check out this BBC Channel 4 documentary that originally aired in August 1999: