I'm currently playing a young supers game with friends using Savage Worlds as our favored system. The plot really hyped them, they loved the first allied extras, and with time they asked me for more characters that can join them in the task of saving the world.
They soon started helping me craft the allies, and then they wanted to know more about them, see them more often, etc. They fear their deaths, and two of them even have a mini fan club between my players.
This happened too with an NPC I crafted that was supposed to be not very important, a girl called Miwako—eventually everyone wanted a piece of her, send her flowers, make her important, be her BFF—and I had to tailor a plot for her that ended up boring me and stealing too much campaign time.
How the NPCs deal with things is becoming more important than how my PCs deal with situations, and the game is becoming "NPC Centric". My players are very interested with the plot, but they're even more interested on hat will happen to their favorite characters and their relationships than what happens with the fate of the world, since everyone on the table seems to think kicking butt is the job of X or Y NPC.
Slowly, the allied extras are stealing the focus of the game, and the fact that my players encourage and wish to see more and more of them makes it harder for me as a GM, especially when everyone wants NPCs galore. I don't want to kill the NPCs out of the blue, nor do I want conflict with my Players, so, what should I do when there's just too much NPC focus?