You're partially right about Agents of S.H.I.E.L.D. explaining it. The episode before the movie came out had Coulson discovering the location of Loki's sceptre and Strucker, then passing the info on to Maria Hill. I would assume she or Tony gathered the Avengers together between that and the movie. They probably didn't show the get-together scene so they could jump into the action immediately.F-I-D-O said:Yeah, that bugged me with the start, especially considering Iron Man 3 seemed to say that Tony Stark would be stepping back from the full Iron Man mode. Maybe Agents of Shield explains it, but the beginning was a tad hand-wavy. Especially considering Shield's collapse in Winter Soldier, it makes me wonder who is actually contacting them. They say Cap's the leader, but I'm not sure how he has Thor's number. Even the "Lullaby" for the Hulk seemed like a relatively practiced element, but there was no in-universe explanation for the reformation.Virtual Boy said:I didn't like how there was no explanation as to why the Avengers were the Avengers again. In the last Avengers movie they all go there separate ways, through the phase 2 they have no interaction throughout all of their individual movies. Then all of a sudden out of nowhere they're a team again with no explanation as to why. I get that they were going after Hydra, but a scene where they reform would have been nice.
That said, the movie quickly made me ignore the reformed team. They had to fight Hydra to address their presence, and it gave a nice setup to Ultron - a problem that demanded the team reunite.
Although . . . now that I think about it, neither the show nor any of the other movies make mention of the team hanging out together on a regular basis, like Age of Ultron implies. Maybe they've been hanging out at Avengers Tower together this whole time? Seems weird, and probably should've been addressed in Winter Soldier at the very least.