User blog comment:Mr. Mittens/Mass Effect: Legacy Trailer- The Adventure Continues!/@comment-3046679-20130516200155/@comment-24174486-20130518160519

It was originally a "parody" of the ending, which for MS means that it had nothing to do with anything that actually happened in the ending save for Koobismo whining about Shepard dying. Then Koobismo decided to make it into an alternate ending which remains true to the lore of the Mass Effect series. Hence Shepard being indoctrinated out of nowhere, Harbinger suddenly having a plan to use Shepard (despite having tried to kill Shepard in every prior encounter and having nearly killed Shepard just then), and the sentient turian husk out of nowhere appearing just in time to usurp the role of protagonist.