"Careful With That Axe, Eugene" went through several incarnations between 1967 and 1969. The earliest known variant is an instrumental called "Keep Smiling, People," from March 1968 that was retitled "Murderistic Women" when it was recorded and broadcast in June 1968 during the band's first post-Syd Barrett John Peel session. (These versions are available only on bootlegs.) The song was expanded and retitled "Careful With That Axe, Eugene" for the B-side of the "Point Me at the Sky" single in December of that year, which later showed up on the singles and rarities compilation Relics. (This title, incidentally, is a reference to the first verse of the now far more obscure "Point Me at the Sky," which is addressed to someone named Eugene.) A few months later, in April 1969, the song appeared under yet another title, "Beset the Creatures of the Deep," as part of the recorded but unreleased live concept performance The Man and the Journey. Then came the best-known version of the song, the crazed nine-minute take that closes side one of Ummagumma, featuring a churning Rick Wright organ solo and some particularly unhinged screaming from Roger Waters in place of the more subtle wordless keening that enhances the earlier studio version. Finally, the basis of "Careful With That Axe, Eugene" showed up one more time as "Come In Number 51, Your Time Is Up," the song at the climax of Antonioni's Zabriskie Point. Of all of these, the spooky but relatively restrained late-1968 studio take remains the definitive version of the song, a dry run for all of the extended instrumental pieces Pink Floyd would compose in the next five years.