This is from this month's Sound-on-Sound, tucked away in an article on the Clavioline (keyboard first made famous by The Tornados on their 1962 song "Telstar" by that account).

Apparently John was feeling "experimental" in the studio that day, and decided that rolling an orange up and down the keyboard was the perfect way to get the sound he wanted. That desperate, almost panicked to my ears, tone has always been one of my favorite Beatles sounds. It sounds almost like the instrument is about to burst!

Trivia for those who may not know but do care (probably not many of those on this forum!) ... this was one of the first songs they recorded outside of Abbey Road. Mick Jagger sang background vocals.

Never liked the song much. Seems to start off sounding ok and then becomes an anti-climax.

We discussed some fact about the song here:
http://dmbeatles.com/forums/b-songs/m-1139216352/s-all/

nothing about oranges from anybody tho....research this time won out....

An orange? It could have been a banana for all we know!
It's a good song but not a milestone hit by any standard.
Good bass & percussion on the track though.