"She Came in Through the Bathroom Window" is a song written by Paul McCartney (although credited to Lennon/McCartney) and performed by The Beatles on their album Abbey Road as part of the Abbey Road medley.
The Beatles recorded the rhythm track for this and Polythene Pam as one on 25 July 1969. It took them 39 attempts, after which they added lead vocals and re-recorded the drums and bass guitar parts.
She came in through the bathroom window
Protected by a silver spoon
But now she sucks her thumb and wanders
By the banks of her own lagoon