Iris is a bright 8-year-old, who lives in New York City, with her big sister named Shorty, a Mami, and a Papi. She also lives with a dog they called El Exigente simply because they all loved him so much. One day they decide to take a trip to the Enchanted State Park. Iris' Aunt Carmen the Beautiful and her brand new husband Juan show up, as does Don Joe who owns the deli.  The whole bunch packs the car with more paraphernalia than they could possibly need.

As everyone climbs into the car, Iris calls for El Exigente to join them, but Shorty protests. Mami and Papi agree that taking the dog on a family picnic is a bad idea. They instruct Iris to leave El Exigente at home.  Iris doesn't know whether to obey or not and she decides to sneak El Exigente into the back of the car! No one notices!

As Shorty predicts, the car breaks down. Papi gets to the business of fixing it. Papi announces that the car is fixed and everyone piles back in, with Iris again smuggling El Exigente aboard. After a short while Papi realizes that he is lost! They seek directions from a Police Officer and  Shorty suggests they write the directions down but she is overruled.  They hit the road and realize that they cannot remember what the Police Officer told them.

Finally, they reach the Enchanted State Park. As they approach, Iris sees the sign... NO DOGS ALLOWED! As they pile out of the car, Iris can no longer control El Exigente who barks and bounds out of the back seat. The stowaway is discovered!!

Iris admits that she smuggled him aboard and. Shorty points out that they have a dog where there are no dogs allowed.  El Exigente's feelings are hurt and he runs away into the theater! Everyone enlists the help of the audience in finding El Exigente. When they do, the whole crew excitedly greets their dog until the question of Iris disobeying her parents is discussed and Iris is forgiven but El Exigente is still not allowed to enter the park. 

They take turns staying with Exigente in the parking lot. In the end, Iris comments that though they had so much trouble, she feels like they spent a terrific day at the park.