Pet as Confidante

Pets can serve as a handy expository device -- especially for films involving a protagonist who spends the bulk of the story alone. Pets help directors effectively establish a lead character without over-relying on narrators, flashbacks, or other contrivances. As the only human survivor in a post-apocalyptic wasteland crawling with mutant zombies, I Am Legend's Robert Neville (Will Smith) relies on his dog Sam to keep him sane -- and to keep us engaged.

See also: Eight Below

Pet as Plot Recycler

A little-known loophole exists in U.S. copyright law that allows for a movie script to deliberately steal plot elements -- or entire storylines -- from previous works, so long as the bulk of the characters in said script happen to be animals. The most recent example of the practice was Beverly Hills Chihuahua, a fairly blatant rip-off of Legally Blonde and, to a lesser extent, Clueless.

See also: The Shaggy Dog, Lady and the Tramp

Pet as Comic Device

This is perhaps the most common petsploitation technique employed by Hollywood. Over the years, pets have proven themselves proficient in a variety of comedic roles, ranging from the subject of short, funny cutaways (Robert De Niro's potty-trained cat in Meet the Parents) to an equal partner in an "odd couple" pairing (see Turner & Hootch and innumerable films like it). And for some strange reason, movie audiences are willing to grant pets much longer leashes when it comes to comedy. Jokes that normally seem trite or hackneyed in the human realm are immediately rendered fresh and inventive when delivered by cute, furry animals. (For numerous examples of this, refer to 2007's Alvin and the Chipmunks.)

See also: Hotel for Dogs

Pet as Therapist

Despite possessing vastly inferior cognitive abilities, animals in petsploitation flicks are often elevated to the status of spiritual gurus, dispensing priceless morsels of wisdom to their befuddled human counterparts. The precocious pup at the center of Marley & Me may spend the bulk of his screen time devouring furniture and urinating on people, but that doesn't stop his owners -- and by extension, the audience -- from revering him as some sort of canine Deepak Chopra.

See also: My Dog Skip

Pet as ATM

Talking-animal flicks provide a great means for so-called "respected" actors to cash in without sacrificing their artistic street cred. Voiceover gigs are relatively undemanding, highly lucrative, and can be easily explained away with the dependable "I just wanted to make something my kids would enjoy" excuse. The most egregious example of this practice came courtesy of Bill Murray, who famously followed up his Oscar-nominated performance in Lost in Translation with the much-maligned Garfield: The Movie. Two years later, he even mailed in a sequel.

See also: Dustin Hoffman in Racing Stripes, Edward James Olmos in Beverly Hills Chihuahua, Nicolas Cage and Penelope Cruz in Disney's upcoming G-Force.

Pet as Sequel Machine

Stars aren't the only folks who've happily boarded the petsploitation gravy train. Studios execs know a cash cow when they see it, too. Disney's 1997 family comedy Air Bud has thus far spawned a staggering seven sequels* -- all of which are basically rooted in America's unending love for golden retrievers dressed in funny people-costumes. And don't forget, pets never hold out for more money. When's the last time the Animal Actor's Guild went on strike?

See also: Beethoven

* The franchise's latest riveting chapter, Space Buddies, arrives on DVD February 3, 2009.