He appears as an antagonist in "When Children Must Be Grown-Ups" when he continuously pulled the Maple Town Train's whistle. The other Maple Town children look after him. He caused multiple aspects of mischief such as messing up the mail letters in the Rabbit Family household and pushing a boulder down the hill at Bobby Bear. He also has a bag containing various possessions such as a picture of his grandmother (referred to as his "treasures").
Kirby is normally mischievous, constantly causing trouble in town. However, it is later shown in his appearance that he actually has a soft side as well, which Patty Rabbit discovers when Kirby told her that he was hungry after pushing a boulder at Bobby Bear (though at first Patty thought that he was sick).
He is a tan and brown tabby cat with whiskers and black beady eyes. He wears a white and yellow-green shirt with a large horizontal stripe, red pants, and brown shoes.