I remember watching "Inside the Actors Studio" hosted by James Lipton when the entire cast of the Simpsons were featured. It was so cool to place faces behind the voices. Here's a video clip:
The Simpsons Cast on "Inside the Actors Studio"
All but a couple play several characters:
Dan Castellaneta plays Homer Simpson, Grampa Simpson, Barney Gumble, Krusty the Clown, Groundskeeper Willie, and Mayor Quimby.
Harry Shearer plays Mr. Burns, Waylon Smithers, Ned Flanders, Principal Skinner, Otto, Reverend Lovejoy, Dr. Julius Hibbert, Kent Brockman, Lenny, and Rainier Wolfcastle/McBain. Cool Sidebar: He is also Derek Smalls in Spinal Tap:
Nancy Cartwright plays Bart Simpson, Nelson Muntz, Rod and Todd Flanders, and Ralph Wiggum. Cool sidebar: Also plays Chuckie on "Rugrats:"
Hank Azaria plays Apu Nahasapeemapetilon, Moe Szyslak, Chief Wiggum, Comic Book Guy, Lou, Carl, Dr. Nick, Snake, Superintendent Chalmers, Professor Frink, and Cletus.
Julie Kavner plays Marge Simpson and Patty and Selma Bouvier. Cool Sidebar: She played Brenda Morgenstern on the "Rhoda" TV
Yeardley Smith plays Lisa Simpson.
Of course, there are other actors, but those are the "big" ones.
Red tail...Red tail...Red tail...Red tail...Red tail...Red tail...Red tail...Red tail...Damned MSP...Red tail...Red tail