- John Lennon – double-tracked vocal, piano, rhythm guitar, talking
- Paul McCartney – harmony vocal, bass, fuzz bass, tambourine, barks
- George Harrison – lead guitar
- Ringo Starr – drums, spoken vocal
Hey Bulldog was first released on the soundtrack album of Yellow Submarine (1969).
John Lennon wrote it as he sat at the piano one day inventing a riff, which then was molded into a song making it one of very few Beatles songs built upon a piano riff. The song was recorded on February 11, 1968, during the Lady Madonna promo video filming - one of the few other Beatles songs wrapped around a piano riff.
The lines initially written as "Hey, Bullfrog" were then changed to "Hey, Bulldog," and the song took its title from that. Paul contributed barking to the recording.
An early demo of the song exists featuring John alone on the piano. The song was titled She Can Talk to Me, and was originally only 47 seconds long.
In the opinion of Geoff Emerick, the long-time recording engineer for the Beatles, Hey Bulldog was the last recording when all four Beatles were still at the top of their game as a unified group and working together in harmony. The next session, in May of 1968 for The White Album, would mark the beginning of the era of personal differences that led to the dissolution of the group two short years later.
The song was inserted into a portion of the Yellow Submarine animation that was included only in the European prints.