Daddy DNA Test

It is discovered that a character, or a baby, has a parent whose identity is not known. Solution? Get a DNA test. Prove beyond a reasonable doubt who the father really is, and proceed from there. All the other guys who aren't the dad can go home. Well, unless the real daddy is a Glorified Sperm Donor and the fake one has actually been there for the kid their whole life. In which case, go take a hike sperm daddy.

Name is technically inaccurate, since this trope can also occur with mothers, but that's a much rarer occurrence, what with the whole she had to be there to give birth to the child and stuff. This test can also be used indirectly to link siblings together. In any case, how long it takes for the DNA test to get finished typically depends on the speed of the plot.

Almost always happens at some point after a Luke, I Might Be Your Father revelation. Also happens if a woman decides to have My Secret Pregnancy. The Trope Breaker for Mama's Baby, Papa's Maybe.

Anime

 * Very irritatingly avoided in Onegai Twins. They explain that it "costs too much money"....the episode before they win a lot of money and blow it on a Hot Springs Episode.

Comic Books

 * In a story arc in Batman: Gotham Knights had the villain Bane discovering evidence suggesting that his real father was an American doctor, and, as the doctor has died, seeking a DNA matching test with the doctor's son -- Bruce Wayne.

Film

 * In Elf to confirm that Buddy was Walter's son.
 * The So Bad It's Good movie Une chance sur deux (Half a Chance): Alice gets a DNA test to find out who her real father is
 * In Ratatouille to see if The testing hit a slight snag when the first sample was identified as "rodent".
 * Baby Mama actually has the inverse with a court ordered maternity test. The premise of the movie was that a surrogate mother is artificially impregnated using the other woman's egg and her own husband's sperm. The test is because she has the child rather late after the egg was inserted and it's unclear who the biological mother is.

Literature

 * Plays an important role in the Adrian Mole series, where a DNA test reveals that Adrian is the father of Glenn Bott, and later that his sister Rosie
 * The Tales of Kolmar series takes place in a medieval world, but it's apparently possible for a demon to confirm who someone's father is.

Live Action TV
"Man, this "Mission Impossible" stuff is great. But other than my scintillating conversational skills, I still don't understand why you brought me along. I need your spit."
 * Used to establish that  in Nip Tuck.
 * House gets a DNA test after his father's funeral, proving that they're not related.
 * One episode revolves around House going to great lengths to prove that his patient's father is not the real father and gets both the parents tested.
 * The titular heroine of Veronica Mars suspects at one point that her real father is her ex-boyfriend Duncan's dad, so she runs a paternity test, which she shreds without reading, deciding she doesn't need to know. Later in the season, Keith Mars has his own test done,.
 * Also done, though not with a DNA test, with Trina Echols, who was adopted. Trina claimed publicly that she needed a bone marrow transplant to smoke out her real parents. Her mother came forward. Her father was a Jerkass.
 * Dorothy and her mom from The Golden Girls.
 * Sidney and Jack Bristow from Alias had to go through this due to speculation that Sidney's biological father was actually Sloane..
 * In My Two Dads, the dads throw away the results, but they needed a little persuading.
 * Often featured on sleazy daytime shows like The Jerry Springer Show, where it's used to determine whether a woman was cheating on her boyfriend/husband with another man or to prove that a man is the father of a child when he denies it.
 * These days every other episode of Maury.
 * Led to a Crowning Moment of Funny when a young mother brought no fewer than a half dozen possible fathers onto the show for testing. After a long drawn-out process of discussing her lifestyle and her complicated parenting situation, the results come back and...none of them are the father! Like a pack of hounds, all the tested would-be fathers round shouting at the girl. "There's even more?!"
 * These days at least once an episode on The Jeremy Kyle Show.
 * In Ugly Betty, Daniel Meade receives a letter telling him he is the father of Daniel Jr., the child of a French model he met years ago on a business trip. The paternity test reveals
 * In Monk, Troy Kroger made his father take three paternity tests because he didn't believe they were related.
 * It's Always Sunny in Philadelphia averts this--Charlie is, more likely than not, Frank's son, but Frank refuses to have the DNA test.
 * A staple of Soap Operas. Count on someone to conceal and/or falsify the results.
 * Used on Lois and Clark when a little boy displayed Kryptonian powers. One guy claimed the test wasn't needed, it must be obvious that Superman is the father.
 * In My Name Is Earl, Earl has Dodge and Earl Jr.'s DNA tested to find out who Dodge's real father is.
 * In an episode of Smallville a woman appears who thinks Clark is her son and demands a DNA test. Clark gets his Secret Keeper Pete to donate a DNA sample after breaking into the lab, so the results won't reveal that Cark isn't human.


 * Dexter has a DNA test done to confirm that the man whose house he inherited was really his birth father.
 * Done confusingly on Gossip Girl in season three with Elizabeth who claims to be Chuck's (supposedly dead) birth mother. Chuck gets a DNA test which proves that she is his mother, but it's implied that the results were tampered with by his Uncle Jack. As of season four we still haven't found out for sure whether or not Elizabeth is his mother.
 * Parodied on Dinosaurs: due to a mix-up, it's suggested that the Sinclairs accidentally got another family's egg (the one that hatched into Baby) while the other family got theirs. Earl and the other father are subjected to battery after battery of bizarre tests (including a centrifuge)... and then the doctor just takes the blood test anyway. The test said the eggs were switched but it was later revealed it was a mistake.
 * Warrick got one on CSI just before his death, as part of his attempt to gain custody of his infant son. His colleagues only discover this when they find the test results while retrieving clothes to bury him in.
 * High-tech alien version occurs in the series finale of Farscape. The fact that Aeryn needs to find out who her baby's daddy is forms a major theme of the final series.
 * Boston Legal: A man who was born out of artificial insemination was dating a woman who was born the same way and they were afraid of being half-siblings. To learn if they had the same father or not, they sued the lab to force them to tell because a DNA test using only the couple's blood would be inconclusive if they were half-siblings or complete strangers.

Web Comic

 * Batman and Sons mentions that Bruce is taking care of baby Terry, but not baby Damien, because  thought to do a DNA test before handing over her kid, whereas Talia did not.
 * Played with on Something Positive, in which a DNA test reveals that Davan is not the father of an ex-girlfiend's son, but Davan and the son bond anyway.
 * A Victorian version on Hark! A Vagrant. (Fourth down)

Western Animation

 * When Homer on The Simpsons wanted to know if his dad was Abe or a lifeguard named Mason Fairbanks.
 * In one episode of The Boondocks, Granddad Freeman goes on a talk show where a DNA test reveals he has a long-lost son.
 * In Gargoyles, Dr. Sevarius performs one on Angela (against her will), and informs her that, biologically, her parents are Goliath and Demona.
 * In South Park, Eric Cartman had no idea of who his father was. Neither did his mother considering the number of possible candidates so a blood test was taken. It was then revealed his father was