I’m trying to come up with a list of trios that kids (up to young teenagers) might know who are. So far I have:
Huey Duey and Louie
Larry Moe and Curly
Greg Peter and Bobby
Marcia Jan and Cindy
Father Son and Holy Ghost
Kirk Spock and McCoy
Harry Ron and Hermione
Athos Porthos and Aramis
And for Epiphany, which is why I need the list:
Melchior Casper and Balthazar
Real or fictional ideas would be greatly appreciated. Thanks.
Shadrach, Meshach and Abednego
Blossom, Bubbles and Buttercup (Powerpuff Girls)
Yakko, Wakko and Dot (Animaniacs)
Ed, Edd and Eddy (eponymous cartoon)
Flora, Fauna and Marryweather (Sleeping Beauty fairies, but featured in some new cartoons more prominently)
Snap, Crackle, Pop (Rice Krispies dudes)
Alvin, Simon, Theodore (chipmunks)
nm, simul-Ninjaed!
Peter Paul and Mary
The Three Amigos(/Caballeros)
Han Leia and Luke
They’ve probably heard of the Three Musketeers, though they’d unlikely know them by name.
Luke, Leia & Han
Jill, Kelly and Sabrina (or whatever they were called in the movie).
Amy, Penny and Bernadette
The Bee Gees
Destiny’s Child
Anne, Emily and Charlotte Bronte
Wendy, Michael and John (the kids from Peter Pan)
Esther, Mordechai, Haman (Story of Purim)
GM, Ford and Chrysler.
BMW, Mercedes and Volkswagen.
Honda, Suzuki and Yamaha.
BSA, Triumph and Norton.
Suzzy Maggie and Terre (Roche)
Geddy Alex and Neil (Rush)
Chad Mike and Mike (Mitchell Trio)
I won a three-horse parlay on them. 
My contribution:
The Three Little Pigs.
The Three Bears–Mama Bear, Papa Bear, and Baby Bear, of the Goldilocks story.
Any of the animals in “Incredible Journey” films: Luath, Bodger, Tao (1963 movie); Chance, Shadow, Sassy (1993 movie).
Manny Moe and Jack (Pep Boys)
Ninja’d on Manny, Moe and Jack (Pep Boys)
Groucho, Chico and Harpo (Marx bros)
The Good, the Bad and the Ugly (from 1966 movie)
Three blind mice
Executive, Legislative, Judicial (branches of sometimes functional government)
Three Strikes Law
Faith, Hope, Charity
Newton’s Laws of Motion
Charlie’s Angels
Nasty, Brutish, and Short
I know, sounds like a law firm.
Past, present, and future
Electron, proton, and neutron
Batman, Superman, Wonder Woman
Chico, Groucho, Harpo
Jack, Janet, and Chrissy
Ferris, Cameron, and Sloane
Charlie’s Angels: Jill, Kelly, and Sabrina or Alex, Dylan, and Natalie depending on what era you’re from
Beyonce Knowles, Kelly Rowland and Michelle Williams
Barry, Maurice, and Robin Gibb
The Good, the Bad, and the Ugly
The butcher, the baker and the candle-stick maker
Larry, Darrell, and Darrell
For that matter, how about Dewey, Cheatham, and Howe, Attorneys-at-Law?
Looking to see if the doper named after the ear bones posted but he did not. So. . .
Malleus, incus, and stapes.
George, George, and Jeb