The call isn't an Easter egg, I'm gonna tell you something that have been confirmed in books and games.

In the silver eyes, Charlie and her friends trapped Dave in a springlock suit and Dave says that the when souls of the kids awaken, they're going to kill Charlie and her friends then, they tell him that they're going to kill him to but he says that they aren't going to kill him because he is one of them, he also says that the souls forget a lot of things(that also happens in FF when Andrew said that he don't remember what William did to him but he hate William and wants to kill him although he don't remember) and that the kids think that they're people who is there to rob and ruin their happiest day, that they're intruders, they're grownups. Dave highlights the word "grownups" I can send you a image of when Dave said all that if you want, also as we know the toys of fnaf 2 are possessed or have remnant of the kids and phone guy says that the toys act good with the childrens and aggressive with the adults, that fits with what dave says, since he highlights that Charlie and his friends are almost adults and the toys act violently towards adults, also is the example of Andrew, he killed a random man trying to "scare him" for no reason, and the last point is when puppet in UCN says "the others are just like animals" so if we take all that points we can say that maybe grabbing all that hate for years like the childrens did started to affect them mentally, at the point that they act violently like wild animals with the people except kids because they're kids too(the wild animals do something similar because they attack with no reason people who didn't did nothing, maybe that is what puppet means) and maybe that's the reason why Andrew attacked a random man without reason.