This trope is about lazily feminized male names or lazily masculinized female names. It's often done in haste or in jest. This trope is focused on the resulting names which are unusual, atypical or downright made up.
It might happen that parents expecting a baby are for some reason convinced it'll be a boy, and they plan to name him after their father, grandfather, or other male relative. Or they simply like the sound or meaning of the male name they chose. But when the kid is born, it's obvious that this specific name isn't quite suitable... because the kid is a girl. Fast forward ten or so years, and little Jamesina is telling people that she was named after her uncle. The parents rightly feel that giving a girl some obviously male name is ridiculous, but they really like the name, so they just add a vaguely feminine-sounding suffix. If it's the other way around, they can just cut the female suffix and change it to the male variant, like swapping Emily to Emil, or Emilia to Emilio.
Another typical use is by pet owners whose animals were previously thought to be males or females. When the animals grow older and mature, their owners realize their cute kitty cat is actually a tomcat, or that their little rooster starts laying eggs. But the pet is already associated with their name and it suits them, so they choose something that is very close, even if it sounds rather absurd.
Sobriquet Sex Switch involves transgender, changed sex, or characters disguised as the opposite sex who go by a name derived from their old one. Examples like Albert and Alberta or "Freddie" (for both Frederic and Frederica) go on that page. Some stranger examples with the lazy aspect cranked up belong here (for example, Bob changing his name to Bobiana is an example of this trope, too). It can be related to Sue Donym — mainly in situations when a character tries to think of a gender-flipped variant of their name on the spot.
This might serve for characterization: lack of imagination or creativity, or just being stubborn and hating to admit the characters were wrong about something. Often done intentionally by characters for the lolz. The trope is almost always Played for Laughs.
Feminine suffixes good for this trope are -a, -ana, -ina, -iana, -ine, -''ella'', -''arella'', -ette, -iette, -etta or -ietta. For Japanese names, -ko is quite common (meaning "child"), but occasionally -mi (meaning "beauty") may also come up. Suffixes for masculine names are not as numerous, but -o, -eo -io, -ino, -iano or -us are sometimes used because many names of Latinate origin end in -o.
Gender-Blender Name is for names thought predominantly as male or female names which are used for the opposite gender. See also Tomboyish Name, Wanted a Son Instead, Last-Minute Baby Naming, Who Names Their Kid "Dude"?, and Embarrassing First Name.
- In Ranma ½, when the protagonists have to improvise a name for Ranma's female form in a hurry to prevent his mother from finding out about his Jusenkyo curse, they instantly jump on "Ranko".
- In an episode of GO-GO Tamagotchi!, Himespetchi wants to act in a movie with her crush Mametchi and disguises herself as a boy to achieve this. The name she assumes as part of the disguise? "Himeboytchi". For added bonus points, "hime" is Japanese for "princess", which begs the question of why Himespetchi didn't think to change that part of her name.
- Dilbert: In the 1994-07-31 strip, the boss tries to give a certificate originally meant for Wally to Alice instead. He hastily corrects the name on the certificate to Alice's supposed "Indian name", "Wallyina".
- Knights of the Dinner Table: When Bob is forced to play a female character, he names her 'Bobarella'.
- Archie Comics: "The Great Switcheroo" issue involved Salem making everyone change sexes. "Archie" gets changed to "Archina".
- In Stage Door, Eve finds out at the end of the movie her cat Henry has just given birth to a litter of kittens. Terry suggests changing the cat's name to Henrietta.
Eve: I'll never put my trust in males again!
- The Disney live-action film The Three Lives of Thomasina has this as part of the Back Story, explaining the titular cat's name. It's hilarious that this mixup occurred with a cat who lived in a veterinarian's home.
Thomasina: They started out by calling me Thomas, but when they, um, got to know me better, they changed it to Thomasina.
- In Alice, Girl from the Future, Iria Gai is a daughter of an inventor who wanted a son as an assistant. He wanted to name him Iriy.
- In the third Captain Underpants book, the three aliens Zorx, Klax, and Jennifer use Human Disguises to pose as new cafeteria ladies, gender-bending their names as part of the guise by adding "-ette" (Zorxette, Klaxette, and Jenniferette) at the end. Played for Laughs in that Jennifer is already a female name by Earth standards.
- Jingo: Denephew Boot's uncomplicated parents were expecting a girl. They wanted to call their daughter Denise ("De-niece"). When trying to masculinise it, instead of going for the obvious choice "Dennis", they swapped "niece" with "nephew".
- In Soul Music, Susan says that "Nigella" means "Oops, we wanted a boy". (Nigel is an English masculine given name, itself not very common, and Nigella is very rare in real life.)
- In Harry Potter, Hagrid acquires a dragon egg and christens the hatchling Norbert. When he sends it to some dragon experts in Romania, they realise it's a female and they rename her Norberta.
- Billina the hen from the Land of Oz series. When she was a chick, her owner, thinking she would grow up to be a rooster, named her Bill. Dorothy adds the '-ina' when she finds out.
- In My Side of the Mountain, Sam befriends a raccoon that he believes to be a male, thus naming him Jesse Coon James. When spring comes, Sam is surprised by the kits, but at least "Jesse" works for a female, too.
- In the book The Six Bullerby Children by Astrid Lindgren, Bosse gets a pet chick who he names Albert, but she turns out to be a hen so he renames her Albertina.
- Sophies Adventures: Sophie names her cat Tom, but then the cat gets pregnant and Sophie considers naming her Thomasina before deciding on Tomboy.
- Dr. Quinn, Medicine Woman: Dr. Quinn recalls that her father expected his fifth child would be finally a boy and planned to name him Michael. When another daughter was born, he decided to call her Michaela.
- Friends: When Ross and Rachel try to find a name for their baby, their friend Phoebe says she has a bunch of great ideas: If it's a girl, Phoebe, and if it's a boy, Phoebo! Rachel jokingly uses these names to ask her ob-gyn whether it's a boy or a girl. Dr. Long later remarks: "And, uh, I know it's really not my place, but please don't name your child Phoebo."
- Hannah Montana: In one episode, the school bully wins a contest to sing with the titular character on TV but Miley and Lily overhear her singing off-key in the girls' bathroom. Miley says that it sounds like her pet pig Lou-Anne and we get this exchange:
Lily: I can't believe it!
Miley: I know, Amber sounds horrible!
Lily: No, I can't believe you had a pet pig named Lou-Anne.
Miley: We thought he was a Lou until the piglets came.
- In Schitt's Creek, her daughter's name Alexis is revealed to be one by Moira, who thought she was going to have a "son called Alex."
- In Sesame Street, Telly names his hamster Chuckie, but she turns out to be a girl, so he renames her Chuckie Sue.
- Stargate SG-1: Someone asks Major Samantha Carter who mostly goes by tomboyish nickname "Sam" what her first name means. She responds, "My father wanted a boy." Safe to assume her father wanted Samuel or Samson.
- In one episode of That '70s Show, Hyde makes fun of Eric by calling him "Erica". Michael who goes by his surname Kelso laughs because you can't do that with "Kelso", at which point Hyde sarcastically points out that he'd be "Michelle". Eric and Kelso then struggle for a few seconds to think of a name for mocking name Hyde ("Hyde-o...lina?"), before he exasperatedly snaps "Heidi!" (Note that Steven Hyde is also on a Last-Name Basis, so he'd be "Stephanie.")
- In Ikemen Vampire, when Arthur got a pet dog from a friend, he made a big show of naming her after Queen Victoria on the spot and didn't realize until he got home that "Victoria" was actually male. Not wanting to admit his mistake, he just shortened his name to "Vic".
- In one episode of The Cramp Twins, Wayne tries joining Marie and Wendy's temporary girl gang by disguising himself as a girl. The name he chose is "Waynona".
- The Fairly OddParents:
- Timmy wishes that Cosmo was a woman and that Wanda was a man. He then names the duo "Cosma" and "Wando".
- Timmy turns into a girl in order to get closer to Trixie. S/he introduces him/herself as "Timantha".
- Looney Tunes: In the short "Mixed Master", a man named Harry brings home a new dog, Robert, but his wife, Alice protests, since the dog appears to be a mutt, and they already have Chang, a purebred Pekinese. Between not being able to figure out what Robert is, and the fact that he seems to clash with Chang, Alice is ready to get rid of him, but Harry insist that they keep him. When Harry comes back home from a business trip, Alice reveals that she found out what Robert really is. Cue Robert coming in with a litter of puppies.
Alice: "Robert" is a mother. Aren't you, Roberta?
- In "Along Came a Sister" of The Loud House, the tarantula is named Frank, but then it turns out to be a girl so she's renamed Frances.
- In the Milly, Molly episode "Sweet Pea", the cops are expecting a baby and the dad suggests naming the baby "Albert Roger" because his wife said, "On Albert [Street]? Roger!". When she turns out to be a girl, he considers naming her "Albertina Rogerilla". Subverted as that idea is rejected in favour of "Daisy Rose".
- In the Dingo Pictures Dinosaur Adventure, Tio's father states that, they were planning on having a daughter named "Tia", and so just flipped the name when they realized they had a son.
- Rocket Monkeys: Gus becomes "Gustina" when he gets turned into a (very ugly) female in "Day of the Doodah".
- The Rocko's Modern Life episode "Kiss Me, I'm Foreign" had Heffer come up with a scheme to prevent Rocko from getting deported back to Australia by claiming Rocko is getting married - to Filburt, who Heffer claims is a female named "Filburta". Filburt, however, prefers the name "Ophelia", and they stick with that.
- The Simpsons:
- "Marge in Chains": Bart's Imagine Spot for breaking Marge out of prison involves him dressed as a woman named "Bartina", romancing the warden, then knocking him out with a crowbar to get the cell keys.
- "Apocalypse Cow": Bart names his calf 'Lulubelle'. Mary suggests he calls him just 'Lou' because he's a young bull. Bart likes it because it rhymes with Moo.
- In Teen Titans Go!, the episode "Fired" has Beast Boy trying to reaudition for his old spot on the team by wearing a Paper-Thin Disguise of a cardboard box with a bikini scrawled on it in marker and calling himself "Beast Babe".