here i copied this....Whatever Gets You Thru The Night took it's title from a TV programme that Lennon had watched about alcoholism, it features Elton John on piano, organ and supplying backing vocals (along with others).
Elton John had much more belief in the quality of the song than Lennon did, and struck up a bet that it would be John's first No.1 ... the payback being that if it did, then Lennon should join Elton at one of his live shows.
In the U.S.A. it duly went to No.1, and Lennon honoured the bet by appearing at Madison Square Garden at an Elton John gig on 28th November 1974. It turned out to be John Lennon's last ever appearance on a public stage, joining Elt on versions of "Whatever Gets You Thru The Night", "Lucy In The Sky With Diamonds", and most poignantly for his last song live, a McCartney song ... "I Saw Her Standing There" which he even dedicated to Paul.