This was simply hilarious, one of the better Shaun The Sheep episodes. I laughed from start-to-finish.
All the sheep except Shuan and the big, fat one have boarded a bus and headed for the nearby carnival. How this could happen in the first place is never explained, but who cares? Well, Shaun does and so does Bitzer, the dog. The latter is responsible for the flock.
While Bitzer goes to find out where they are and get them back, Shaun has to disguise the fact they are missing to the farmer, who periodically looks out his window to see that everything is okay.
Shaun's ingenuity is excellent (and humorous) and Bitzer's reactions to all that is going on his also very funny. Funniest of all, however, were the sheep at the carnival. Some of the scenes are guaranteed to make you laugh out loud!