Seems John just couldn't keep his hands off other peoples stuff. From http://dir.salon.com/story/ent/music/feature/2003/01/27/paul_yoko/index2.html

In 1972, as part of their "Sometime in New York City" album, Ono and Lennon released four live tracks recorded at the Fillmore East with Frank Zappa and the Mothers of Invention. One track, the Mothers' standard "King Kong," was retitled "Jamrag" by John and Yoko, who inexplicably took full songwriting credit. Zappa remained miffed for years, telling Rolling Stone in 1988: "I can't imagine that album really sold a lot; anyway, it's the principle of the thing, you know?"

Interesting. It reminded me of Give Peace A Chance: http://www.dmbeatles.com/forums/b-lennon/m-1135782215/

Interesting. It's not a new thing though, nicking the odd tune from an obscure song and hoping to get away with it. Noel Gallagher's 'Whatever', for instance, is a rip off of Neil Innes's 'How Sweet To Be An Idiot'. I remember the confusion about who copied who in the 70's with Bowies 'Gene Genie', and The Sweet's 'Blockbuster'. In effect, they probably both nicked the riff from the same obscure song.

Then theres the whole saga with 'Come together' and 'you cant catch me'...........