The origins of Monty Python's Parrot Sketch have been well documented, but on the eve of the team's imminent reunion I think they could stand a little more examination. And as the cowriter of Freddie Davies' autobiography Funny Bones, to be published by Scratching Shed on July 31st, I may be able to add a further note.
The essence of the joke has been traced back to Ancient Greece but let's begin a little later, with Michael Palin's supremely evasive car salesman (above) in a sketch in the one-off pre-Python show How to Irritate People; if you are unfamiliar with it you can see it here.
As is well known to aficionados, that situation was reworked for a Python sketch with the garage replaced by a pet shop and, at Graham Chapman's suggestion, a parrot replaced the car as the faulty object. (At one point a toaster had also been mooted, which suggests it took a while for the shop's identity to settle.)
You will find occasional references online to the idea being stolen from Freddie "Parrotface" Davies. That would be getting rather silly, as the late Colonel Chapman might have put it. Nevertheless, it's not beyond the bounds of possibility that Freddie's standup act may have made a small contribution towards this enduring sketch.