Insert Character A into Show B

Sometimes mixing things up in unexpected ways is the royal road to genius: Think of the first guy to put peanut butter next to jelly, or gin next to tonic. Sometimes it’s a really, really bad idea, like the time I ignored my mechanic’s advice and added a quart of maple syrup to my car’s engine instead of motor oil.

The same is true of TV shows. George Clooney and Noah Wyle once showed up as their "ER"characters on a particularly funny episode of "Friends." Bob Newhart found a perfect way to end his 1980s sitcom by realizing the entire series had been just a dream of the character Newhart played in his 1970s sitcom. But there are plenty of crossovers that just shouldn’t happen, no matter how tempting they may seem. Here are seven of them.

The mate was a mighty sailin' man
Character: Rupert Boneham, "Survivor"

Show:  "Gilligan’s Island"

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Moves in when: A clerical error strands Rupert on an uncharted desert isle, but not the one where he was scheduled to be.

What happens: His bearded wild-man looks and admirable skill at roughing it endear him to the Skipper, Ginger and all the other castaways. He becomes especially good friends with the Professor, from whom he learns much about crafting high-tech modern conveniences out of coconuts and palm fronds.

Why he leaves: He’s voted off the island in the first round because the others think he’s a sure bet to win the million dollars. The ultimate winner is Thurston Howell III, who chucks the prize money in his vault with the rest of his wealth.

To the 'Moon,' Andy
Character: Andy Rooney ("60 Minutes")

Show:  "Sailor Moon"

Moves in when: The success of the movie "Lost in Translation" leads CBS executives to create a new series pairing the world’s most cantankerous television commentator with the hyperkinetically perky, super-powered teenage girl of the cult-classic Japanese anime.

What happens: Andy isn’t much help at solving the persistent boyfriend troubles of Sailor Moon and her miniskirted fellow Sailor Scouts. But when Queen Beryl of the Negaverse invades Earth and the Sailor Scouts can’t stop her with their usual Mercury Bubble Freeze and Cosmic Moon Power attacks, Rooney saves the day by complaining petulantly about something he saw on the back of a cereal box, boring the villains to death.

Why he leaves: Rooney quits in favor of another animated series, taking a job as replacement for Grandpa on "The Simpsons." He pops in at the end of each episode to tell a rambling, self-indulgent anecdote with no point, the same thing he’s been doing on 60 Minutes for years.

KITT becomes a legal eagle
Character: KITT the talking car, "Knight Rider"

Show:  "Ally McBeal"

Moves in when: At loose ends after David Hasselhoff moves on to lifeguard duty in "Baywatch," his four-wheeled sidekick drives himself over to Harvard Law School, gets a degree, and takes a job as a defense attorney at the law firm of Cage & Fish.

What happens: He fits right in. Compared to the baby-hallucinators, wattle-fetishists and other eccentrics around the office, a talking Trans Am with a bulletproof paint job and a computer brain is almost normal. In order to ease KITT into the firm’s social life, the unisex toilets where half the storylines took place are moved down to the parking garage.

Why he leaves: Tragedy strikes during KITT’s very first session in court, when the judge orders the courtroom sealed during a sensitive case. KITT leaves his engine running, and a lack of proper ventilation causes massive carbon-monoxide poisoning.

Dr. Kramer

Character: Cosmo Kramer ("Seinfeld")

Show:  "ER"

Moves in when: Even though he has no medical training of any kind, Kramer is hired as a consulting internist after the Journal of the American Medical Association publishes his account of curing a patient’s infection by dropping a Junior Mint inside his body during surgery.

What happens: At first, Dr. Carter and the other "ER"regulars attribute Kramer’s unorthodox diagnoses to eccentric genius. But even when they begin to suspect he’s just a hipster doofus, they keep him on staff because they’re impressed by his ability to pretend to have gonorrhea and cirrhosis of the liver.

Why he leaves: His incompetence is revealed when he fails to save the stricken Cage & Fish law firm from massive carbon-monoxide poisoning. He is last seen driving away in a black sports car with a flashing red light on the grille and a license plate reading “ASSMAN.”

That meddlin' Monk
Character: Adrian Monk ("Monk")

Show:  "Scooby Doo"

Moves in when: Obsessive-compulsive detective Adrian Monk befriends the crime-solving Great Dane (who, of course, refers to him as “Radrian Ronk”). Since he’s already phobic about germs, heights, flying and a thousand other things, the idea of a case involving a mummy or a vampire involves no special difficulty for him.

What happens: Monk’s brilliant logical mind is no match for the class of criminals usually investigated by the Scooby Gang. Once he figures out that all you have to do is walk up to the “monster” and pull off the rubber mask to reveal Mr. Jenkins, the gardener who seemed innocent at the beginning of the show, the crime rate drops to zero within a fifty-mile radius.

Why he leaves: Monk is freaked out by Shaggy’s unkempt appearance, and hyperventilates at the thought of what kind of germs might be thriving in the back of the Mystery Machine. But the final straw comes when a well-meaning Velma rewards Monk for a job well done by popping a handful of dog treats in his mouth.

Simon says Kirk
Character: James T. Kirk ("Star Trek")

Show:  "American Idol"

Moves in when: The 24^th century’s most emotive starship captain goes through a time warp around the Sun’s gravity well so that he can prove to the world what a terrific singing voice he has.

What happens: Kirk’s wildly bombastic rendition of “Lucy in the Sky With Diamonds” goes over with the judges like a photon torpedo.

Why he leaves: Humiliated by the blunt sarcasm of Idol’s hard-to-impress Simon Cowell, Kirk beams back to his own time. Cowell goes with him, and eventually becomes the leader of the Klingon Empire, his reign of terror built on his ability to make even the most battle-hardened warrior cry.

Ms. Smith Goes to Washington
Character: Anna Nicole Smith ("The Anna Nicole Show") and Ozzy Osbourne ("The Osbournes")

Show:  "The West Wing"

Moves in when: In a shocking upset during the next presidential election, voters toss out Josiah Bartlett in favor of reality TV’s most reality-challenged stars. The two run jointly as a single candidate so that they can more effectively share the remaining brain cell left between them.

What happens: The State of the Union speech reaches historic new highs for rambling incoherence and must be [BLEEP]ed more than 350 times; beating the previous record set by Warren G. Harding. Ozzy gives a particularly graphic demonstration of his support for federal budget cuts by biting off the head of a bat. After the speech, Anna Nicole hosts a blowout afterparty at the Lincoln Memorial and passes out in the statue’s lap.

Why he leaves: One day, the co-presidents are inadvertently left alone with the launch codes for the U.S. nuclear arsenal. Anyone who’s ever secretly thought that reality TV might be a harbinger of the apocalypse is proven right.

Christopher Bahn is a writer in Minneapolis.

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