In the movie, Frou-Frou is the horse of Madame Bonfamille and a friend of Duchess and her kittens. In the beginning, she gives Madame, Duchess, and the kittens a ride back home from town and she allows one of the kittens to ride on her back to which Berlioz thanks her for when they arrive at home. When Edgar the butler realizes that the cats will get Madame's fortune when she dies, he kidnaps them and takes them out into the countryside. When Madame wakes up in the middle of the night and discovers the cats missing, she runs screaming, "Duchess! Kittens! They're gone!" This wakes Roquefort up and he goes out to search for them.
When Roquefort returns, he goes to see Frou-Frou in the barn and she asks them if he found them to which Roquefort replies that he didn't. Frou-Frou also informs him that Madame didn't sleep either after she found out that Duchess and the kittens were gone. They are surprised when Edgar arrives in an unusually cheerful mood. He reveals to Frou-Frou that he's the catnapper because he made the headlines in the newspaper. This disgusts her and Roquefort who hiding on top of her head. But then Edgar realizes that he lost his hat and umbrella behind and that could lead to evidence with him being the catnapper and that he needs to get those things back tonight. After Edgar leaves Frou-Frou and Roquefort come with a plan that Roquefort will hop on Edgar's motorcycle and ride along with him to get his hat and umbrella back and that will possibly lead Roquefort to where Duchess and her kittens. However, when Roquefort hops on, he accidentally bounces off as Edgar rides away like a maniac.
The next day when Duchess and the kittens return home with the help of an alley cat named Thomas O'Malley, a shocked but determined Edgar traps Duchess and the kittens in a trunk and prepares to ship them to Timbuktu. But when he's about to push them outside, O'Malley jumps on Edgar's back and Frou-Frou grabs his coat tails with her teeth, but he manages to pull away from her. Still, she manages to block him from pushing the trunk outside with her front legs. Edgar chases O'Malley into a pile of hay and nearly stabs him to death with a pitchfork, much to Frou-Frou's horror. Then O'Malley's friends Scat Cat and his gang of Alley Cats show up and help free Duchess and her kittens. The cats trap Edgar by trapping him in Frou-Frou's horse collar, throwing a bucket of water on his head and hoisting him up on a rope. Finally, Frou-Frou kicks Edgar with her back hooves, sending him into the trunk. Then Frou-Frou and the cats watch as Edgar is shipped off to Timbuktu in the cats' place. In the end when Madame opens up her house for all the alley cats, including Scat Cat and his gang of alley cats, Frou-Frou appears singing "Everybody Wants to Be a Cat".
She could be named after Frou-Frou, Vronsky's steeplechase mare in Anna Karenina.
Frou-Frou with Berlioz
Frou-Frou with Madame
Frou-Frou and Roquefort sad that Duchess and the kittens are out of Madame's mansion
Frou Frou and Roquefort see Edgar arriving, in an unusually cheerful mood.
Frou-Frou glares at Edgar
Frou-Frou whinnies as Edgar whacks her with his newspaper.
Frou-Frou protecting Duchess and her children from Edgar
Frou-Frou frightened and upset that Edgar left Thomas arrested on the wall
Frou-Frou pulling the rope to put Edgar in the Timbuktu's box
Frou-Frou preparing to kick Edgar to the Timbuktu's box
Frou-Frou, Roquefort and Alley cats happy that Edgar is going to live in Timbuktu