As deep and abiding as it is, the friendship is defined by the differences in their lives in a way familiar to many men in their thirties. One is settled down, with a wife and a child, ensconced in a quiet neighborhood (sleepy Crouch End, where McAvoy lives with his wife of eight years, Anne-Marie Duff, and their son, who turns 4 in June). The other is still in the messy bachelor pad he's had for years (Fassbender's been meaning to spruce up his apartment in an edgy corner of Hackney ever since he moved there in his twenties). Both have demanding jobs. So they text, send each other videos, and are thick as thieves when working, as they were while filming X-Men: Days of Future Past in Montreal. And off set—let's just say that their outings still feel like something of an occasion.