For such a short and silly song, "Why Don't We Do It In The Road?" was responsible for a considerable amount of inter-Beatle acrimony. John and George were engrossed in finishing off some other songs as The White
sessions were drawing to a close, so Paul — bored again — shut himself away in another studio and began to bang it off by himself. Literally: the percussive intro was him thumping on the soundbox of his acoustic, though he did invite Ringo to provide a real drum part (and a few extra handclaps) the following day.
John was mightily miffed to've been excluded, taking it both as a personal slight and a massive manifestation of McCartney megalomania (though on a separate occasion he qualified the song as "one of his best"). Paul played the whole thing down (the kerfuffle, not
the track!) speculating that, as it was "a very John" sort of song, he was merely put out at not having had chance to get in on the act: and he probably had a point, given that JL never publicly grumbled about all the other McSolos on the record. Mind you, I'm quite sure that he would've had a fine old time hamming it up as a duet, had the opportunity arisen.
Nevertheless, Macca it was who handled all the parts of the increasingly raucous vocal, and he really didn't seem to have required any assistance, at the end of the day...
The recurring question had first arisen after he'd spotted two monkeys shagging in the middle of a path in the Maharishi's camp (real ones, not John and Yoko, 'cos she wasn't there anyway...). Minimalist though the lyric may have been — only four more words in the whole thing than just the title of Lennon's monkey song
— the musical accompaniment was as meticulous as one would expect from Macca. He did actually play his acoustic, as well as just bashing it: along with the bass, piano and electric lead.
Turning it into a bawdy boogie-woogie blues, rather than sticking to the acoustic Anthology approach certainly seemed more appropriate to the subject matter:No one will be watching us —
Why don't we do it in the road?!!