Benny first appears when Eddie Valiant and Roger Rabbit escape from Judge Doom and the Toon Patrol in the bar and then encounter him locked up in their paddy wagon for driving on a sidewalk, despite going for a few miles as claimed by him. They free him and he helps them get away, taking them to a movie theater to hide.
He later appears when Eddie and Jessica Rabbit are trying to flee from the Toon Patrol and again tries to help them out, but this time, the dark and cruel Judge Doom spills Dip across the road he drives along, injuring him and making him skid off the road and crash into a pole. After Eddie and Jessica are taken hostage, he lies still, recovering, and joins up with Roger when he happens to pass by in Eddie's car, taking over the job of driving and explaining to Roger what's just happened. He drops him off at the Acme factory and drives off to find help.
He is last shown at the end of the film in the Acme factory, listening with Dolores, Lt. Santino, and some human policemen about what Eddie found out about Judge Doom and rejoicing over the discovery of Marvin Acme's will.
Benny also made frequent appearances in the Roger Rabbit comics.
According to the movie, Benny has been a cab for 37 years. Since the movie takes place in 1947, one can assume that he has done so since 1910.
Benny is the only toon to be exposed to Dip and survive. This could be because while other toons, like Judge Doom and Smarty, were fully exposed from head to toe, Benny was only hit at the bottom of his tires. This exposure did, however, leave him weak and limping.
In the novel Who Censored Roger Rabbit, Benny (spelled Bennie) was a beetle (the insect, not the car).