Rose proves to be a freeloader, eating up a lot of the food (such as consuming a turkey that was supposed to be for the Higgenbottoms) and starts using objects belonging to Bessie. What's more, she is a negative influence on Happy, convincing him to steal for example.
She attempts to steal steaks, but is caught by Bessie and Ben, before ultimately being revealed as an impostor and not Happy's mother after all. Rose is voiced by Dee Bradley Baker, though he went uncredited for the role.
After Bessie, Ben and Happy had given up on searching for Happy's mother, Rose arrived and showed them she had a red heart shaped birthmark, just like Happy's mother. Thus, the Higgenbottoms believe her to be his mother and Happy is thrilled to reunite with his mom. He licks Rose's face to signify his happiness.
When Ben and Bessie ask questions about Happy's early life, she isn't straightforward with them, giving the two simple answers (i.e., that Happy was small as a puppy) and breaks into hysterics when Bessie wonders how she and Happy became separated. She takes Bessie's desk without permission and uses it as a bed.
Although she and Happy enjoy drinking from the toilet and howling at the moon, she starts influencing Happy in a negative way, namely stealing a customer's steak at Hilary's Cafe and encouraging him to play poker in the basement.
Bessie chastises Happy when she finds out, with Rose mocking her behind Bessie's back. Then, she overhears Hilary ordering t-bones, and hatches a plan with Happy: that he pose as Hilary while she steals several steaks from the driver's truck.
The plan fails when Bessie and Ben catch her in the act, mentioning Happy told them the plot. As Happy is no longer on her side, she runs away frantically, only to slip on the Higgenbottom home's wet floor and smash into a bucket of water. The water from the bucket on Rose’s head causes Rose's supposed birthmark to wash away, revealing her to be a liar and not Happy's mother. She is kicked out of the house by Hilary, falling down the street all the while.
Rose looks similar to Happy, being a dark blue dog with a purple nose and white hair. Her muzzle and stomach are a light shade of gray. She has black dog ears and a tail of the same color, in addition to a yellow collar. The collar in question has a gold circle on it, emblazoned with her name.
- It is never revealed what is inside Rose's handbag.
- She has a cat coat, which implies she may have killed a cat.