When a sitcom kills off a major character, it's almost always promoted aggressively by the network.
For instance, Fox's Animation Domination block features the long-running animated sitcom The Simpsons, and when they kill a major character at the beginning of next season, it will be after more than a year of fans knowing it was coming.
Tonight, though, Family Guy killed off Brian Griffin--the family dog, yes, but arguably one of the show's two most prominent characters (along with Stewie), it seemed like it would be resolved by the end of the episode (after all, Stewie has a time machine that he's used on more than one occasion, and he and Brian have hopped through the Multiverse before). It didn't happen, though, and the family replaced him with a new dog, who ended the episode bonding with Stewie after he broke down about having lost his best friend.
Social media...didn't take it well. Here's a sampling.
Family guy is done!!! The new dog doesnt cut brians role-.- #FamilyGuy
— OLLIE (@AllUGHVer) November 25, 2013
OMG. HE'S DEAD. #FamilyGuy — Terrence | C.O.G (@Nerd_Sage) November 25, 2013
That's the end of Brian.... Dear Jeezus I'm crying #familyguy — Ahlea Y. (@Leuh2219) November 25, 2013
Wow. I can't believe Seth MacFarlane killed off Brian. #FamilyGuy
— Bryan Kerver (@BKerver1994) November 25, 2013
This is the saddest thing I've ever seen. How could you kill off Brian? #FamilyGuy
— Scott Akos (@AkosScott) November 25, 2013
So the they really killed off Brian. They got a new dog. Stewie didn't go back and save Brian. The episodes over. Im #blown #FamilyGuy
— Harrison Baxter (@HollaBaxta) November 25, 2013
What. The. Fxck. ???? It's just gon end like that??? #FamilyGuy @FamilyGuyonFOX there better be a part 2 :((((
— Pam J. W. (@LoveSingPray) November 25, 2013
Well they killed Brian... And replaced him with a crappy Italian stereotype.... Awful just awful #familyguy— Matt Trifoso (@tryyyeefoso) November 25, 2013
HOW do u kill Brian, and the duo that is Stewie and Brian? How does the show continue past that? #omg #familyguy— Lisa Flaugh (@FlaughlessLady) November 25, 2013