"Boris the Spider" was written after Entwistle had been out drinking with the Rolling Stones' bass guitarist, Bill Wyman.
According to Pete Townshend in his song-by-song review of Meaty Beaty Big and Bouncy for Rolling Stone, it was Jimi Hendrix's favourite Who song.
This recording was eventually released on the 1995 and 2009 reissues of The Who Sell Out (immediately after their cover of "In the Hall of the Mountain King"), and at the end of their BBC Sessions disc.
They created similar jingles to the tune of "My Generation" and "Happy Jack" (available on BBC Sessions and Thirty Years of Maximum R&B, respectively).
"My Size", the opening track of Entwistle's 1971 solo album Smash Your Head Against the Wall, is a sequel to "Boris the Spider.