Diane Simmons was a supporting character in Family Guy and the hidden main antagonist in the episode "And Then There Were Fewer".
Role in Family Guy
She used to work for the Channel 5 News alongside Tom Tucker for most of the series, being very calm and kindful in nature. It remained that way until in "And Then There Were Fewer", when she previously dated James Woods until recently when she turned 40. She was then scheduled to be replaced by a younger woman thanks to Tom Tucker, and James Woods dumped her. At that point, Diane turned mad & insane and secretly swore revenge against both James Woods and Tom Tucker.
Diane, along with all the other main and recurring Family Guy characters, was invited to a dinner party in their honor. Little did any of them know that it was James Woods who invited them, in an attempt to make peace with them all for wronging them in life. All of James's dinner guests sat down at the large table in the dining room, but when James had to go into the kitchen, Quagmire's date, Stephanie, sat in James's chair. When Brian attempted to open a bottle, the cork flew off. As soon as the cork flew off the bottle, Stephanie's chest turned red, and died. Diane had set a timer that, when the time ran out, would trigger a gun to fire at James's chair.
With her initial attempt of murder of James Woods failed, a series of events took place which resulted in the murders of four more people. Upon Diane realizing her mistake and everyone's suspense towards Woods over Stephanie's death, a power outage comes, and Diane took the opportunity to finally kill Woods without everyone looking. When four of the guests start to learn more towards her nature, she brutally kills them to cover her tracks while pretending to be scared along with other guests. Diane would later plant Priscilla's corpse and a Golden Globe she used to kill Derek Wilcox inside Tom's room, making everyone implicate Tom as the killer, leading him to be arrested. Delighted that she finally got her revenge against both Tom and Woods, Diane was about to go home, but Lois Griffin later finds out about her muderous nature, inciting Diane to murder her. While on a cliff, which lead to the ocean below, Diane attempted to shoot Lois, but was shot to her death by Stewie from a balcony of James Woods' mansion, who then told himself that he holds the rights to murder Lois and nobody else. Eventually, her murderous plot and death later became revealed to the public in the subsequent episode "Excellence in Broadcasting", and Tom is finally released to go back working for Channel 5 with Diane's replacement, Joyce Kinney.
Diane and the other characters deaths were considered canon by Seth MacFarlane, and have not been seen in the show since.