Sam Simon - producer, character designer, and creative supervisor on The Simpsons. Creator of many of the residents of Springfield (Mr. Burns, etc.)
Matt Groening. God.
Bill Oakley - Simpsons writer and showrunner. (Co-wrote "Lisa vs. Malibu Stacy" and "Who Shot Mr. Burns" and many more episodes w/ writing partner Josh Weinstein.)
Josh Weinstein - Simpsons writer and showrunner. (Co-wrote "Lisa vs. Malibu Stacy" and "Who Shot Mr. Burns" and many more episodes w/ writing partner Bill Oakley.)
Conan O'Brien - Simpsons writer and supervising producer. First new writer hired after launch of the show. Writer of "Marge Vs. the Monorail". Namer of Jub Jub. Currents whereabouts unknown.
David Silverman - Simpsons director ("Bart Gets an F", "The Way We Was", etc) and director of The Simpsons Movie. Largely credited with establishing the 'rules' for drawing/animating Simpsons characters. Later co-director of Pixar's "Monsters, Inc."
Jim Brooks - Developer/executive producer of The Simpsons, writer/director of Terms of Endearment, writer for The Mary Tyler Moore Show, co-creator of "Taxi". Used his clout in Hollywood to bring The Simpsons to life.
Al Jean - writer, executive producer and showrunner on The Simpsons. With writing partner Mike Reiss, wrote episodes "Stark Raving Dad" and "Lisa's Pony".
John Vitti - Simpsons writer. Wrote "Lisa's Substitute", "Burns Verkaufen der Kraftwerk", "Radio Bart" and "Mr. Plow", among many other episodes.
Mike Reiss - Simpsons writer. With writing partner Al Jean, Reiss wrote episodes "Stark Raving Dad" and "Lisa's Pony".
John Swartzwelder - insanely prolific Simpsons writer, having penned over 50 episodes including "Bart Gets Hit By A Car", "Dog of Death" and "Krusty Gets Cancelled". He now writes books about time travel and other fun stuff.
Wallace Wolordarsky - Simpsons writer. Co-wrote "Bart the Daredevil", "Treehouse of Horror I" and "Lisa the Greek". Later writer of DreamWorks' "Monsters Vs. Aliens" and actor in several Wes Anderson flicks.
Greg Daniels - Simpsons writer and executive producer. Wrote "Homer and Apu", "Bart Sells His Soul" and "Lisa's Wedding". Later a writer for Seinfield, and writer/co-creator of King of the Hill. Now a writer/director/co-creator of NBC's version of The Office.
Dave Mirkin - Simpsons writer, executive producer and showrunner. Writer of "Deep Space Homer". Later a director of The Larry Sanders Show and co-creator (with Chris Elliott) of "Get A Life".
George Meyer - Simpsons writer and producer. Wrote "Homer the Heretic" and creator of 'Army Man', a self-published 'zine which John Vitti and John Swartzwelder wrote for. Credited with helping shape the Simpsons' writing style during the early years of the show.
Jeff Martin - Simpsons writer. Wrote "Oh Brother, Where Art Thou?", "Three Men and a Comic Book", I Married Marge" and "Homer's Barbershop Quartet" among other episodes.
Brad Bird - executive consultant/director on The Simpsons. Writer and director of The Iron Giant and The Incredibles.
Something I whipped up to celebrate the 20th anniversary of the airing
of the first Simpsons episode, way back on December 17th, 1989
("Simpsons Roasting on an Open Fire", for those keeping
track at home.)
Apologies for any likenesses/credits I may've messed up, or for anyone
I may've missed.