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. This trope can also occur with mothers, but that's a much rarer occurrence (barring a babynapping, a switcheroo with a different newborn, or a delivery while the woman is unconscious, the mother knows the baby she just birthed is her own). 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. The DNA test could present complications: if the bad guys know about the test, they may attempt to keep the Status Quo by altering the test results (of course, they must force other characters into secrecy about that, and in any case it won't last for long). May result in a Surprise Incest, if the character was in a love relation with an offspring of the man who turned out to be the father. 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.
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- Very irritatingly avoided in Please 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.
- In Mobile Suit Gundam Wing: Endless Waltz, Mariemaia claims that Treize being her father has been confirmed through DNA testing. We never actually see the results of the test though, and there is considerable doubt on Mariemaia's parentage all the same.
- 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.
- A variation in H'el on Earth When Superman puts his battle-suit on Superboy, the family crest should have changed the instant it identified his Kryptonian bloodline. It stayed the same, confirming Superman's suspicions that Superboy's his clone.
- Done in Elf to confirm that Buddy is 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 but she likes the two possible dads so much that she throws away the results.
- In Ratatouille to see if Linguini is Gusteau's son. 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.
- 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 is the daughter of their mother's ex-lover Mr Lucas.
- 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.
- In Maeve Binchy's Minding Frankie, the hero tests if he really is the father of the eponymous Frankie. He finds out he is not, then decides the DNA result does not matter, he is her father in every way that matters.
Live Action TV
- Used to establish that Christian is the father of Matt in Nip/Tuck.
- House gets a DNA test after his father's funeral, proving that they're not related. Given that they had an extremely tempestuous relationship House is relieved to find this out.
- 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. Turns out both aren't his biological parents and he's adopted.
- House also performs a paternity test on one of his 'friends' and his current patient, who told him she's his estranged daughter from an old fling. House tells the kid that his friend is her father, but the test result House gets later on turns out to be negative.
- Another episode has House trying to prove that at least one of Taub's kids isn't his. Eventually Taub gets the results, but shreds them without looking.
- 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, which confirms that he is, after all, her real father.
- 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 Jerk Ass.
- 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. Turns out Jack is her real father.
- 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 that Daniel Jr.'s father is Alexis Meade, now Daniel's sister.
- In the Monk episode "Mr. Monk Gets a New Shrink," Dr. Kroger is revealed to have a stormy relationship with his son Troy. Namely, because Troy has made him take three paternity tests because he didn't believe they were related. Also, Randy has arrested Troy on at least one or two previous occasions.
- 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. The boy's mother claimed that Superman was the father, while a shocked Superman protests that he's never seen her before, let alone slept with her. One guy claimed the test wasn't needed, it must be obvious that Superman is the father. The boy was human, and the super powers had been transferred to him.
- In My Name Is Earl, Earl has Dodge and Earl Jr.'s DNA tested to find out who Dodge's real father is. It turns out it was him all the time. Earl and Joy conceived Dodge at a Halloween party. It's also revealed that Earl Jr.'s real father is not Darnell as was previously thought. It's never revealed who his father actually is. Word of God says Earl Jr.'s father was supposed to be someone famous, but due to the series' cancellation, they never got to do that plotline.
- 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.
Pete: Man, this "Mission Impossible" stuff is great. But other than my scintillating conversational skills, I still don't understand why you brought me along.Clark I need your spit.
- 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.
- Earlier, Aeryn is convinced that an alien is her long-lost father via high-tech DNA test. The test results were actually faked.
- 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.
- On NCIS, Abby tests her DNA against the DNA of the woman that she thought was her mother and finds out that she's adopted.
- Drives the plot of the Firefly episode "Heart of Gold." At the titular bordello, a local petty tyrant forcibly takes a DNA sample from the unborn child of one of the prostitutes, promising to return for the child if it's his (and it is, of course). The madame hires the crew of Serenity to help drive him off.
- Batman and Sons mentions that Bruce is taking care of baby Terry, but not baby Damien, because Catwoman thought to do a DNA test before handing over her kid, whereas Talia keeps Damian to herself and just keeps sending him bills.
- In Something*Positive, Davan has Sex for Solace with the ex-girlfriend of his friend who recently committed suicide. Years later, the two meet up again and Davan finds out she had a son named Rory, whose father is either Davan or the man she dated shortly after their tryst. The test shows that Davan isn't the father, but Law of Inverse Paternity kicks in and he becomes Rory's Parental Substitute anyway.
- A Victorian version on Hark! A Vagrant. (Fourth down)
- When Homer on The Simpsons wanted to know if his dad was Abe or a lifeguard named Mason Fairbanks. He wasn't, but Abe switched the labels because Homer seemed too interested in 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. Except the host lies about the test results on camera, only putting a disclaimer in the credits. The man's real father is Billy Dee Williams.
- In Gargoyles, Dr. Sevarius does a DNA test on Angela (against her will) and happens to discover that Goliath is her biological father. This shocks her and winds up causing some drama, since Goliath follows the gargoyle tradition where biological relationships aren't important.
- In South Park, Eric Cartman had no idea 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 his "mother", who was actually a hermaphrodite who had a penis (much to the disgust of the men who only learned when Dr. Mephisto brought it up) and impregnated some woman. Cartman briefly asked who his real mother was, much to the horror of the men who believed they could have been his Dad, but, once Ms. Crabtree the school bus driver, Principal Victoria and the Mayor of South Park were introduced as options, Cartman decided he didn't want to know.
- Of course many many seasons later it was revealed that The whole thing was a ruse, Cartman's mother is actually biologically female, and Cartman's father is Scott Tenorman's father, who Cartman had killed and tricked Scott into eating in a bowl of chili.