Please give us Yanks the etymology of guernsey.
It's fairly complicated. Both Jersey and Gurnsey (the two largest of the Channel Islands) were famous for their lightweight woollens, originally made to keep the crews of their fishing fleets warm and dry. There was considerable rivalry between the islands over who made the better and finer knitwear.
Back in the days before artificial fibres, these light-weight knitted shirts were particularly prized for sporting apparel, and a team shirt became known as a "Jersey" in England, and as a "Gurnsey" in Ireland. They both brought their teminology to Australia, where (particularly in Victoria, where a version of Gaelic Football became Australian Rules Football), being selected for your local football team was referred to as "getting a Gurnsey".
That phrase has broadened in scope to mean being selected for almost any position, but particularly one that entails joining a group endeavour.
In this case,
@Tigers! is expressing surprise that neither Obama was given a place in the cast of the movie. He wasn't expecting them to be granted ownership of any of the Channel Islands.