Simpson's characters who have died (excluding 'Tree House of Horror' episodes):
Died & stayed dead:
Mona Simpson
Maude Flanders (fall at racetrack)
Frank Grimes(electrocuted)
Bleeding Gums Murphy(heart problems)
Truckdriver Red Barclay(beef posioning)
Beatrice Simmons (heart attack)
Moe's Professor at Swigmore U (drowns himself)
Marge's Aunt Gladys(bowel obstruction)
Asa Phelps (third to last of the Flying Hellfish)
Amber Simpson (Homer's Vegas wife)
Mrs. Glick
Edna Krabapple (Unknown Cause of Death)
Chip Davis
Presumed Dead but Returned:
Dr Nick Riviera (died in movie)
Dr Marvin Monroe (Showed up in Diatribe of a Mad Housewife telling Marge he had been very sick)
Known Dead:
-Francis Griffin (Peter's Dad, Peter crushes him)
-Thelma Griffin (Peter's Mom, Died of Stroke)
-Joan (Peters maid and Quagmires ex-wife, killed by Death)
-New Brian (Brian's replacement, chopped to pieces by Stewie)
-Mr. Jonathan Weed (Peter's boss at the Happy Go Lucky Toy Factory, choked on a dinner roll)
-Vern & Johnny (Vaudeville performers, shot by Stewie)
-Derek Wilcox (Jillian's Husband, killed by Diane)
-Muriel Goldman (Mort's wife, stabbed by Diane Simmons)
-Diane Simmons (Shot by Stewie, then fell off a cliff)
-Nigel Pinchley (Hung by British authorities)
-Jeremy (Liddane the babysitter's boyfriend, Left in truck of car to die by Stewie)
-Bertram (Shot with a crossbow to the head and chest by Stewie)
-A future version of Mort Goldman (killed by Stewie in the time machine)
-Loretta Brown (although technically she died on The Cleveland Show)
-Uncle Chet (Cleveland's Uncle, died in his sleep)
-Amy (The girl Death had a crush on her, He just killed her)
-Drunk Billy (Channel 5's News Chopper pilot)
-Big Fat Paulie (Shot in a Mob drive by)
-Aunt Marguerite (Lois' Aunt, Natural Causes)
-Peter Griffin Jr. (Shaken to death by Peter as a baby)
-Vanessa Griffin (Chris' future wife, killed by Stewie although that timeline no longer exists so her death is moot)
-Naomi & Dale Robinson (Car crash)
-The Man in White along with his cult members
-Colin Farrell (Shot by Stewie)
-Super Devil (Accidentally shot by Brian)
-Stephanie (Glen's one time girlfriend, killed by Diane)
-Priscilla (James Woods' wife, killed by Diane)
-Unnamed Valet (Blown up by a car bomb)
Also one time characters named, Howard, Gerald and an unnamed stripper
Presumed Dead:
-Paddy Tanniger (Presumed dead when run over by a tank)
-Matthew McConaughey (Shot with a arrow by Stewie)
-Ms. Hobson (Stewie's day care teacher, shot by Stewie with arrow)
-Joan Cusack (Peter crushes her and throws her away)
Do you mean which actress died who worked on Family Guy?
If so, none of the female cast members have died. Guest stars like Phyllis Diller and Carrie Fisher have passed away, they voiced Thelma Griffin & Angela respectively but they obviously weren't part of the cast.
You might be thinking of Mary Kay Bergman who worked on South Park. She committed suicide in 1999 also, Marcia Wallace died in 2013. She voiced Edna Krabapple on The Simpsons.
Quite a few actually. Most notably... Peter's parents Francis & Thelma.
Diane Simmons, Muriel Goldman, Jillian's husband Derek, Bertram, Cleveland's ex-wife Loretta, and many more.
See this site (familyguy.wikia.com/wiki/Category:Deceased) for a complete list.
The most recent "death" was Stan's Dad, Jack. He was killed by Santa but was changed into Krampus.
There was an episode called 100 A.D. where they killed off 100 minor recurring & one time characters. Some of those were...
• Brett Morris (Dope and Faith)
• Dr. Meg Penner (Wife Insurance)
• Mr. Kerkhoff (Delorean Story-An)
• Beauregard LaFontaine (Star Trek & Irregarding Steve)
• Belmonpan (Meter Made)
• Paco (American Dream Factory)
• Coco (One Little Word)
• Alejandro Roja (Wife Insurance)
• Clifford (Of Ice & Men)
• Bobby the Bullet (Stannie Get Your Gun)
• Gertie (Roger Codger)
• Ted Feedler (Threat Levels)
• Pillow Hands McGraw (Threat Levels)
• Bjorn (I Can't Stan You)
• Katie (Not Particularly Desperate Housewives)
• Ray (42-Year-Old Virgin)
• Matty Moyer (Stanny Slickers 2: The Legend of Ollie's Gold)
• Duper (Roger Codger) (Although his clone lives on)
Brian was killed in the 6th episode of Season 12, Life of Brian.
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In the 8th episode, Christmas Guy, Stewie altered the time line saving Brian from getting killed by the car thus returning him to the show.
Family Guy - 1999 Mom's the Word 12-12 was released on: USA: 9 March 2014
(May 2012) Obviously since Season 10 just ended. Season 11 will start September 2012 & end in May 2013 with Season 12 airing the following September and end in May 2014. It has not been renewed after that.
Season 1 Episode 5 - 29:12
Season 5 Episode 12
No, Olivia Benson is alive and well for season 12 and through the current season.
No. He did not appear in Season 12.
December 09th 2014
Yes Season 12 concluded on May 18th 2014.
season 4 episode 12
Family Guy - 1999 To Love and Die in Dixie 3-12 is rated/received certificates of: USA:TV-14
December 9, 2014
September 29, 2013 and ended on May 18, 2014
Season 6|Episode 12 Long John Peter
Season 10|Episode 12 Livin' On A Prayer
Airport '07 Season 5 episode 12
Family Guy - 1999 Christmas Guy 12-8 was released on: USA: 15 December 2013
Family Guy - 1999 Christmas Guy 12-8 is rated/received certificates of: USA:TV-14