Diane Simmons (née Seidelman) was Tom Tucker's co-anchor on Quahog 5 News. Although when the series started, she and Tom seemed to have a healthy and at times possibly sexual relationship, that quickly changed to where they instead bicker a lot on the air, and she soon became the butt of his jokes. This relationship started spiraling around the time of her 40th birthday. She also hosted a talk show called Diane!, on which the Griffins were guests and exposed their secrets. The show was first seen in "Fifteen Minutes of Shame".
In "Patriot Games", it was revealed that she once had a husband, before he committed suicide, as commented once by Tom on the air, causing her to break down crying. She admits to being a bit of a bigot, such as once openly joking on the air that she is racist against black people, though she believed they were off the air since Peter Griffin had cut off Quahog's television signal. During the Special People's Games in "Ready, Willing, and Disabled" she and Tom commented together how watching the game would give them all a sick sort of laugh, and how all of them were most likely going to hell for it.
In "The King Is Dead", it was revealed that Diane's maiden name is "Seidelman". Simmons is also a dedicated actress having done some pretentious student films in college. At one point, she was set to play the role of Anna in The King and I having stolen the role from Loretta Brown, during Lois Griffin's first theatrical production. Unfortunately, Peter Griffin, who stole control of the show from Lois as producer, later changed the script so massively much that even Diane couldn't stand the direction the show was taking and quit. Peter took over the role personally, turning Anna from a British female school teacher, into a male, cybernetic assassin from the future.
In "Da Boom", Tom and Diane eat Asian reporter Tricia Takanawa, although this event was non-canonical.
In "And Then There Were Fewer", Diane reveals she has turned 40, and becomes the murderer of James Woods, Muriel Goldman, Derek Wilcox, Priscilla and Stephanie. She explains her plan to murder Woods and frame her co-anchor, Tom Tucker to Lois, nearly murdering her as well. It was revealed that she dated Woods and Tom successfully convinced the network to replace her at the news desk, as well as Woods dumping Diane, which resulted in Diane to seek vengance. However, before pulling the trigger, she is shot and killed by Stewie and falls off of a cliff to her death, Stewie then declares only he is allowed to kill Lois. In a message on his Twitter account, Seth MacFarlane confirmed that the episode was canon and that Diane is dead, and so are the characters that were murdered.
Murders committed by Diane Simmons
- Stephanie - Set up a firearm to cook off and pointed it at the head seat at the table. Stephanie was an unintended victim, as the bullet was intended for James Woods, who was to sit at the head of the table.
- James Woods - Stabbed during a power outage in revenge for him dumping her.
- Muriel Goldman - Stabbed for discovering that she is the murderer of Stephanie and James Woods.
- Derek Wilcox - Bludgeoned with a blunt object as he had attempted to summon first responders for help. The blow to Derek caused him to fall off the veranda, so it appears more likely his actual cause of death was defenestration.
- Priscilla - Had her throat slit for seeing her with the knife and becoming hysterical. Her body was planted in Tucker's room, along with the blunt object used to strike Derek, in an attempt to frame Tucker for the murders.
- Lois Griffin (attempted) - She attempts to kill Lois to keep anyone from finding out she had killed the previous victims, but just before she pulled the trigger, Stewie Griffin shot her with a sniper rifle, and tumbled off a cliff into the ocean.