Everyone would recognize Homer J Simpson if he walked down the street but would you recognize the man behind the face.

Dan Castellaneta

Homer Simpson
Grampa Simpson
Santa's Little Helper
Barney Gumble
Krusty The Clown
Groundskeeper Willie
Mayor Quimby
Hans Moleman
Sideshow Mel
Itchy
Gil
Big Rich Texan
Lance Murdock
Arnie Pie
Kodos
Scott Christian
Squeaky-Voice Teen
Mr. Teeny
Leopold
Gary (the nerd)
Bill (from KBBL)
Freddy Quimby
Burns' Lawyer
Poochie
Bill Clinton (AABF08)

Julie Kavner
Marge Simpson
Patty Bouvier
Selma Bouvier
Jacqueline Bouvier
Aunt Gladys

Yeardley Smith
Lisa Simpson
Lisa Jr. (BABF11)

Nancy Cartwright
Bart Simpson
Nelson Muntz
Todd Flanders
Ralph Wiggum
Kearney
Database (from Superfriends)

Hank Azaria
Apu Nahasapeemapetilon
Moe Szyslak
Chief Wiggum
Comic Book Guy
Lou
Carl
Dr Nick Riviera
Snake
Kirk Van Houten
Captain McCallister
Bumblebee Man
Superintendent Chalmers
Professor Frink
Cletus
Legs (mafia)
Akira
Luigi
Doug (the nerd)
Raphael (Sarcastic Clerk)
Duffman
Pyro (a.k.a. Chase)
Drederick Tatum
Gabbo
Brad Goodman
Dean Peterson
Frank Grimes
Shelbyville Milhouse
Knightboat
Arthur Fortune

Harry Shearer
Mr. Burns
Waylon Smithers
Ned Flanders
Principal Skinner
Otto
Reverend Lovejoy
Dr Hibbert
Kent Brockman
Jasper
Lenny
Eddie (the policeman)
Rainier Wolfcastle (McBain)
Scratchy
Kang
Mr. Bouvier (Marge's father)
Dr. Marvin Monroe
Herman
Mr. Largo
Marty (from KBBL)
Dr Loren J Pryor
Jebediah Springfield
Judge Snyder
Sanjay (Apu's brother)
Nigel (B Sharps manager)
George Bush
Birch Barlow
The real Sgt. Seymour Skinner (4F23)
Bill Clinton (AABF09)

Russi Taylor
Martin Prince
Uter
Sherri/Terri
Lewis
Wendell

Pamela Hayden
Milhouse Van Houten
Rod Flanders
Janey Powell
Jimbo Jones
Sarah Wiggum
Ham (from Superfriends)
Ms. Pennycandy (Krusty's assistant)

Tress Macneile
Dolph
Sunday School Teacher
Brandine
Agnes Skinner
Adil Hoxha
Shelby
Pepi
Barbara Bush (3F09)
Lester

Marcia Wallace
Edna Krebappel

Doris Grau
Lunchlady Doris
Lurleen Lumpkin (when she reappears in 9F10)

Maggie Roswell
Maude Flanders
Helen Lovejoy
Miss Hoover
Luann Van Houten
Princess Kashmir
Shary Bobbins
Kindergarten teacher
Barbara Bush (8F01)

Kelsey Grammar
Sideshow Bob

Joe Mantegna
Fat Tony.