In the film Marmaduke, Owen Wilson and George Lopez are the main characters portraying a dog and a cat. The Great Dane will start off living in Kansas when his owner Phil is transferred to an office in Orange County. The dog and cat will move into a new home when Phil will find out what he was transferred to Orange County for. He will be given the task of making sure that Bark Organic gets stocked in every Petco around the country. Phil will meet with Don, his boss at a dog park. While at the dog park, Marmaduke will meet a gorgeous Collie by the name of Jezebel. Jezebel will have a boyfriend by the name of Bosco.
Marmaduke will meet some new friends who will meet at night to crash parties at pedigree only homes such as Bosco's. They will be scared away by the brut when Marmaduke asks his friend if she can help him to get a girlfriend. Mazie will assume that he is talking about her however he is referring to Jezebel.
Marmaduke will get Carlos, the cat, to pretend that he is missing in the dog park. A staged fight will occur in order for Marmaduke to pretend that he is tougher than he really is. He will enter into a surfing contest where his owner has decided to use this as a promotional stunt to get Petco to sign a contract stocking Bark Organic into their stores. Bosco is a well established surfing champion and this will cause the two to become enraged with one another when a fight breaks out. This no doubt sends Petco representatives running.
Marmaduke will end up taking Jezebel on a dream date that Mazie thought of. She will watch him from afar. When the Winslow family is out on the boat with Don, Marmaduke will throw a party with most of the dogs who attend the park attending the party. Bosco will then in turn crash his party. This is when he realizes that it was Carlos at the dog park. Bosco will point it out to the rest of the party goers who will leave Marmaduke with no friends. Phil comes home only to discover a trashed home. Marmaduke finds himself locked outside for the evening. This causes him to run away. He will come across a dog who has the reputation of killing his owner when in reality all he did was run away. He will give Marmaduke some advice and then distracts the dog catcher so that Marmaduke does not get caught.
The next morning the family will find Marmaduke missing and start searching to find him. An accident will cause Mazie to fall into the rainwater conduit after the street has collapsed causing Marmaduke to jump in to rescue her. Phil and the fire department will attempt to retrieve him. They will get Mazie out but will loose Marmaduke. Phil will then be fired for missing the meeting with Petco. He will then find Marmaduke and convince him to let go of a tree branch he is holding onto only to be carried away by the waters where he ends up making it to Phil. The whole thing is caught on tape and uploaded to YouTube. The video will be such a big hit that Phil will regain his job. Because of the video, Petco ultimately decides to hire Bark Organic.