In the movie, she is voiced by Bebe Neuwirth, best known for her portrayal of Dr. Lilith Sternin on the NBC television sitcom, Cheers and its spinoff, Fraiser.
Sylvia appears to be a young female dog with a small snout and short lush red hair. Her most common seen outfit is a white button top with a black shirt, wearing a pair of red frame glasses over her dark green eyes. Sylvia also wears a black skirt and 1970s-style black heels.Later on, when dancing with Goofy, she is seen wearing a 1970's inspired outfit, colored mostly green, complete with gold hoop earrings and a large red afro-like hairstyle. She also has removed her glasses and has light purple eyeshadow.
While she is seen as the quiet and well-mannered librarian of the college Max and Goofy attends, she is shown to be a fun loving and sweet woman on the outside, quickly revealed by Goofy upon meeting her. She is a fan of old collectibles and shows, same as Goofy, and loves to dance. Eventually, she falls in love for Goofy and is seen as his girlfriend after their first "date" together. Sylvia is also shown to be very affectionate and spontaneous, as shown when she smothered Goofy multiple kisses after finding the flowers he bought her.
She is shown to have a cold side to her, seen when Goofy accidentally forgot their date when he felt disheartened from Max rejecting him. Since then, she remained cold and distant from Goofy when they met again, though this later faded away after Goofy pleaded for her help. She also values family bonds as she watches in hope at the changes transpiring between Max and Goofy throughout the movie.
At one point, Sylia pins Goofy down and kisses him all over this face, leaving red lipstick marks. This is similar to what Minnie Mouse and Daisy Duck do to Mickey Mouse and Donald Duck respectively in various cartoon shorts.