The name is explained in song. Romero is from his father's best man, Miguel is from his father, Junipero is from his mom's favorite brother and Francisco Quintero is from the minister who married his parents.
In 1940s comics, his full name was originally given as El Gayo José Francisco Sandro de Lima y la Loma Pancho Allegre.
And in promotional materials for the original film, it was Panchito Pistoles, the one short name he's ever had.
The Simpsons: Selma Bouvier Terwilliger Hutz McClure thought that adding Nahasapeemapetilon was a stretch too far. Didn't stop her adding Stu later, though...
Also Apu Nahasapeemapetilon himself.
Oovilu-Eeoo-Kitana-Wanjay. Also called Lisa Jr. by Homer Simpson.
One episode shows Rainier Wolfcastle's first TV appearance, in a commercial in his native Austria. The following is sung to the tune of the Oscar Meyer song.
Mein bratwusrst has a first name,
Mein bratwurst has a second name,
The woman whose got constantly interrupted by Oxy Moron speaker in the mock commercial...thing in Sheep in the Big City has a really long name: Smythe Robertson Johnson Weathermocker Von Herbertson-Berski-Jackson.
In one of the minor sketches on the show, we have a man named Ivanovich Malkovich Ivanich Fiftyskitch Fallsinaditch Thatsagoodpitch Romanov. But since he's friends with the female character, he tells her "There's no need to call me by my FORMAL name...Just call me Ivanovich...Malkovich Ivanich Fiftyskitch Fallsinaditch Thatsagoodpitch. You can leave out the 'Romanov' bit." To which the female character responds with "Oh, thank you Ivan...ahem...thanks!"
When the female character's fiancee caught her with Ivanovich Malkovich Ivanich Fiftyskitch Fallsinaditch Thatsagoodpitch Romanov, he said he didn't believe to see her being that close to his best friend, to which Ivanovich Malkovich Ivanich Fiftyskitch Fallsinaditch Thatsagoodpitch Romanov said he wasn't the fiancee's best friend. The fiancee then referenced Romanov as someone he calls by the twenty first names.
Rabbit Ears Productions had a VHS series of American and world folktales. From New England came the tale of sea captain Stormalong, who previously served under Captain Phineas Elijah Jeremiah Ebenezer Josiah Cheever Gesundheit.
In the SpongeBob SquarePants episode "One Krabs' Trash", Smitty Werbenhickermanjensen was the name of the guy who owned the soda drink hat. It isn't quite as long as others but it's long enough to not fit on his headstone.
In one of the earlier episodes of Avatar: The Last Airbender, Aang gives the alias "Bonzu Pippinpadaloxicopolis III" to a city guard whilst disguised as an old man. Katara picks up on this immediately with "hi...June Pippinpadaloxicolopis, nice to meet you."
One episode of Chowder involved a game known in full as "Field Tournament Style Up-and-Down On the Ground Manja Flanja Blanja Banja Ishka Bibble Babble Flabble Doma Roma Floma Boma Jingle Jangle Every Angle Bricka Bracka Flacka Stacka Two Ton Rerun Free for All Big Ball." Mung Daal believed it brings bad luck to call the game by anything other than its full name.
Oh, you mean Aloyse Everheart Elizabeth Otto Wolfgang Hypatia Gunther Galen Gary Cooper von Roddenstein?
Watching Family Guy and seeing "Cherry Chevapravatdumrong" in the credits, you might be tempted to think that's a deliberate application of the trope, but no, it's the Real Life name of a Thai-American co-producer and story editor on the show.
Lampshaded when a character was introduced to replace Diane Simmons and given that name, but says she changed it because "they'd never let that name on television."
Lois' sister, Carol Pewterschmidt Johnson Carrington Stone O'Craggity Canseco Shteinholtz Washington Proudfoot Fong West.
In the Hansel & Gretel episode of HBO's "Happily Ever After", the stepmother tells them to refer to her as "Mrs. Hernandez de la Torrez del Balboa"
While they weren't that extraordinarily long taken individually, the names of characters in the Schoolhouse Rock installment on pronouns (Rufus Xavier Sarsaprilla, Rafaella Gabriela Sarsaprilla, Albert Andreas Armadillo) are repeated in full so many times in the song that they seem like this trope. Which is deliberate, the better to convince kids that Some Pronouns Need to Be Dropped.
Total Drama has several: Harold's full name is Harold Norbert Cheever Doris McGrady V, Cody is Cody Emmett Jameson-Anderson, and Blaineley is Mildred Stacey Andrews-O'Halloran.
According to his toy bio, the full name of the character DJ from Cars is Devon Montgomery Johnston III.
Other cars with long names include Winford Bradford Rutherford, Richard Clayton Kensington, Antonio Veloce Eccellente, and Costanza Della Corsa.
The full name of the main character from El Tigre, Manuel Pablo Gutierrez O'Brian Equihua Rivera.
After becoming furious over the very obviously racist South Park flag in "Chef Goes Nanners", Chef's personality morphs into full-blown Malcolm Xerox mode, going as far to, among other outrageous antics, dropping his "slave name" and adopting his new "Muslim" name: Abdul Mohammad Jabar-Rauf Kareem Ali. Because it won't fit on his uniform, he has to have someone else hold up a banner with the rest of the name printed on it standing right next to him.
On Danger Mouse, Dr. Augustus P. Crumhorn's lengthy real name has Barry Manilow in it.
In The Treacle People, there is a Scottish character who goes by the name of Alistair Ocintoshin McMurdo of the Clan McMurdo of Ayr & Frune. He insists on always being called this, though the rest of the characters just call him "Digger", with Silas Mitten occasionally referring to him as McMurdo.