Shirley is a member of The Flock lead by Shaun. She is by far the biggest sheep of the flock, and sports a ferocious appetite. Although Shirley has what to many is an intimidating appearance, she has been shown to be a very caring sheep, who always stays at the side of the flock. She plays a predominant role in the series, Appearing in the majority of episodes and even being named in the Series 6 trailer.

Shirley has been shown to be fond of Timmy, and she fiercely protects him from danger, such as whenever The Fox tries to kidnap him.