Mystery Inc. (Fred, Daphne, Velma, Shaggy and Scooby-Doo) attend the opening of an exhibition at the Coolsonian Criminology Museum commemorating their past solved cases with monster costumes on display. However, the celebrations are interrupted by the Evil Masked Figure who steals two costumes using the reanimated Pterodactyl Ghost. The gang are ridiculed by journalist Heather Jasper Howe who starts a smear campaign against them. Concluding an old enemy is the mastermind, the gang revisit old cases, dismissing the former Pterodactyl Ghost, Jonathan Jacobo, due to his death during a failed prison escape, they guess Jeremiah Wickles, the Black Knight Ghost’s portrayer, is the culprit.
Lucky the dog (Norm Macdonald) explains Dr. John Dolittle's (Eddie Murphy) gift of talking to animals. John comes home from France and gives his wife a present from Paris. He also gives his daughter, Maya (Kyla Pratt), a chameleon, named Pepito.
Artist Jennifer Spencer and her sister are raped by a group of boys, after being betrayed by female friend Ray Parkins. The brutal rape leaves Jennifer's sister permanently catatonic. Ten years later, Spencer seeks revenge. She kills one of the rapists (George Wilburn) with two shots—one in the groin and one in the head—from a .38 snubnosed revolver. Spencer then leaves San Francisco because of the subsequent police investigation. Once relocated in the town of San Paulo, Spencer begins restoring its boardwalk's historic carousel near the beach where the rapes occurred.
In Beverly Hills, California, wealthy heiress Vivian "Viv" Ashe leaves her richly pampered pet chihuahua, Chloe, with her irresponsible niece, Rachel, while she embarks on a business trip for ten days. Papi, the gardener Sam's pet Chihuahua of Mexican descent, has an unrequited crush on Chloe, by which she is disgusted. Rachel decides to go to Mexico with her friends and stay at a hotel by the beach. When Rachel leaves Chloe alone in the hotel room to go dancing at a club, Chloe goes looking for her. Chloe gets dog-napped as she tries to find Rachel and is sent to the dog fights in Mexico City. There, she meets a street-smart German Shepherd named Delgado. Rachel comes back to the hotel and is frantic when she finds Chloe missing.
When the film opens, a St. Bernard puppy and a large group of others are stolen from a pet store by two thieves, Harvey (Oliver Platt) and Vernon (Stanley Tucci). After meeting a dog during his escape from the thieves, the St. Bernard sneaks into the home of the Newton family. The workaholic father, George Newton (Charles Grodin), doesn't want the responsibility of owning a dog, but his wife, Alice (Bonnie Hunt), and their children, Ryce, Ted and Emily, convince him otherwise. While trying to name him, Emily (Sarah Rose Karr), plays a portion of Ludwig van Beethoven's Fifth Symphony and he barks along: thus they name him "Beethoven."
Jon Arbuckle (played by Breckin Meyer) plans to propose to his girlfriend Dr. Liz Wilson (played by Jennifer Love Hewitt), who is going on a business trip to London. Jon follows her to the United Kingdom as a surprise; After escaping from the kennel, Garfield (voiced by Bill Murray) and Odie sneak into Jon's luggage and join him on the trip. Garfield and Odie break out of the hotel room, then get lost.
John Brown is a humble, but clumsy security guard working at the Bradford robotics laboratory in Riverton, Ohio, run by Artemus Bradford and his daughter Brenda, whom Brown has a crush on. Brown wishes to become a police officer, with support from his niece Penny. Brenda and Artemus create a lifelike robotic foot as part of the Gadget Program, to create cybernetically augmented police officers. Tycoon Sanford Scolex attacks the lab, steals the foot, and has Artemus murdered before escaping in his limo. Brown goes chasing him down in his car, which leads to its being destroyed by Scolex's explosive cigar leaving brown for dead, but a bowling ball coming from the fiery blast of Brown’s destroyed car smashingly crushes Scolex's hand, forcing him to replace it with a mechanical claw.
In 1927, silent film star George Valentin is posing for pictures outside the premiere of his latest hit film when a young woman, Peppy Miller, accidentally bumps into him. Valentin reacts with humor to the accident and shows off with Peppy for the cameras. The next day, Peppy finds herself on the front page of Variety with the headline "Who's That Girl?" Later, Peppy auditions as a dancer and is spotted by Valentin, who insists that she have a part in Kinograph Studios' next production, despite objections from the studio boss, Al Zimmer. While performing a scene in which they dance together, Valentin and Peppy show great chemistry, despite her being merely an extra. With a little guidance from Valentin (he draws a beauty spot on her, which will eventually be her trademark, after finding her in his dressing room), Peppy slowly rises through the industry, earning more prominent starring roles.
Astérix and Obélix have to win the Olympic Games in order to help their friend Lovesix (Stéphane Rousseau) marry Princess Irina (portrayed by Vanessa Hessler). Brutus (Benoît Poelvoorde) uses every trick in the book to have his own team win the game, and get rid of his father Julius Caesar (Alain Delon) in the process, but fails.
Infuriated by belittlements, Queen Cleopatra makes a deal with Julius Caesar: if the Egyptians build a palace larger than Caesar's palace in Rome in three months, he must acknowledge that Egypt was the greatest of nations. To perform this task, Cleopatra hires the architect Numerobis, on pain of death and much to the dismay of Pyradonis, Cleoptara's customary architect. He and his secretary Papyris discuss the druid Getafix (Panoramix in the original French), whose potion empowers its drinkers; and Numerobis goes in search of him.
On the streets of Fifth Avenue, an orphaned kitten named Oliver is left abandoned after his fellow orphaned kittens are adopted by passersby. Wandering the streets by himself in search of someone to adopt him, Oliver meets a laid-back dog named Dodger who assists the kitten in stealing food from a hot dog vendor named Louie. Dodger then flees the scene without sharing his bounty with Oliver. Oliver follows Dodger all throughout the streets until he eventually arrives at the barge of his owner, a pickpocket named Fagin, along with his meal, to give to his friends: Tito the Chihuahua, Einstein the Great Dane, Rita the Saluki and Francis the Bulldog. Oliver sneaks into their home, located below the city's docks, and is discovered by the dogs. After a moment of confusion, Oliver is then received with a warm welcome. Fagin, owner of the dogs, comes in and explains that he is running out of time to repay the money he borrowed from Sykes, a ruthless shipyard agent and loan shark. Sykes tells Fagin the money must be paid in three days, or else. Sykes' Dobermans Roscoe and DeSoto attack Oliver but the cat is defended by Fagin's dogs. Immediately thereafter, a depressed Fagin returns to the barge, lamenting that he has only three days to find the money he owes Sykes. After the dogs cheer him up, Fagin is introduced to Oliver, and, considering that they all need help, accepts him into the gang.
In 1993, Jerry Shepard (Paul Walker) is a guide at an Antarctica research base under contract with the National Science Foundation. UCLA professor, Dr. Davis McClaren (Bruce Greenwood), arrives at the base. He presses Shepard to take him to Mount Melbourne to attempt to find a rare meteorite from the planet Mercury. Shepard does so, ignoring his own intuition, which tells him it is too late in the season to complete such a treacherous route, and decides that the only way to get to Mount Melbourne is by dog sled.
The film begins in the home of the Newton family, where George, Alice, their three children, and Beethoven are all well adjusted to living together. Beethoven sneaks out and meets Missy, a female St. Bernard whose owners are attempting to settle a divorce. Regina, who is seeking $50,000 in the settlement, has retained full custody of Missy and only plans to transfer her to Brillo, her soon-to-be ex-husband, once the divorce is finalized.
While in Central City, Louisiana, orphans Andi (Emma Roberts) and Bruce (Jake T. Austin) manage to sell a rock in a box to a pawn shop to buy food for their dog, Friday, a Jack Russell Terrier. However, they are quickly caught and marched off to the police station, where their social worker, Bernie Wilkins (Don Cheadle) picks them up and takes them back to their foster parents, Lois and Carl Scudder (Lisa Kudrow and Kevin Dillon, respectively), who appear not to care for either Andi or Bruce. When the two demand to know where their foster children have been, Bernie covers for them, telling them that it was his fault they were late. Despite his sympathies towards the two siblings, he warns them that they are playing a dangerous game by deliberately getting into trouble in order to escape Carl and Lois, since they could get fostered separately, something that both orphans are desperate to avoid. During Bernie's visit, Friday returns home and Bruce quickly bustles Bernie out of the door, since Friday's presence is to be kept secret.
At a satellite base in Northern Germany, a worker named Freidrich, who is delivering secret codes finds a Cocker Spaniel puppy outside his office. He takes the puppy inside and shows it to his Bloodhound Rex. Rex senses that something is wrong with the dog and barks at it, making the worker take him outside. Both get locked out of the office. Rex looks through the window and sees the puppy taking pictures of the secret codes and revealing itself to be an evil female hairless Sphynx cat named Kitty Galore in disguise. Rex turns out to be a dog agent and reports to HQ.