so...E. астра, астер spells Easter...in case people didn't know...but they made it out to be different...so whats the E stand for?

I kinda think Ты should ask Bunnymund himself или any really "professional" fan. (I'm kinda am. Haha!) But even I don't know.
Could Ты try posting this Вопрос on Rise of the Guardians Фан Club instead? Maybe Ты could get еще Ответы this way.

I'm not really sure, to be honest. I know there's a book about Rise of the Guardians, so it might be in there или maybe the movie trivia (there might be some on IMDb). I just know its an initial. :) Btw, they were really clever with the names in the movie XD