Mac is a tall, thin, and white-coloured hen with brown tips on her hackle and thigh feathers. She wears a long plaid scarf and thick glasses; that of which is held in place by a metal band surrounding the top of her head.
Her long, maroon-coloured comb sticks out from this metal band in different directions giving a sort of messy look, similar to the leaves of a palm tree. She appears to have small buck teeth that locks her into an awkward grin on her face. Her beak and legs are a light orange-yellow colour.
Mac is the most academically intelligent of the chickens. She helps Ginger plan out their escape attempts by offering her knowledge of aerodynamics, anatomy, mechanics, and other sciences to achieve this.
Because of her thick accent and her heavy use of technical jargon, she can be quite difficult to understand at first hand; such as times when Rocky struggled to understand her, but the other chickens could (as they have probably been around her longer.)
Generally she is one of the more calmer characters and does not seem to freak out as openly when faced with a problem; compared to others. She speaks with a levelheaded tone to her voice while usually remaining unassertive and expressionless.
Despite this, she is not afraid to stand up for others when needed to- such as when she stood up for Babs later in the movie. Her aggressive side is rarely shown but when she is pushed to the limit it can be quite out of control, such as when Bunty was picking a fight with her and had to be stopped by Fowler.
However overall she can be dependable and kind, and is a big dreamer just like Ginger, constantly inventing things that would be seen out of a chicken's ability to do so.
- Early in development, Mac's name was supposed to be short for McNugget.
- According to the pattern of the scarf she is wearing, Mac belongs to clan MacLeod of Lewis, Scotland.
- Mac's thick glasses are a reference to the similar glasses worn by Dustin Hoffman in Papillon (1973).
- Mac is able to play the harmonica, and at one point provides the background music for several seconds.
- During the escape scene at the end of Chicken Run. Mac says I canny work miracles captain! We're givin' her all she's got! and later when Fowler shouts Great Scott! What was that? Which then Mac replies A Klingon captain! The engines cannae take it This is a reference to the Star Trek character, Scotty, who like Mac is also Scottish.
- Mac is intentionally supposed to be hard to understand as a joke, but in reality she just talks really fast in her accent, along with a few Scottish expressions thrown in on occasion.