Ironically, I think most people are "spoiled" by certain things because of all the people screaming spoiler at them. I mean,
take a picture of you-know-who in red for example. One could simply think "Oh, hey. He got new armor. Cool!"
but if people keep screaming SPOILER ZOMG!!!111!!WTFBBQ!!~ they know something is up.
Same with
Nidhogg. I mean, come on did you REALLY think he would be that easy to kill in the Aery? They don't tell you how he came back in a picture unless it's a picture of Est turning into him =p