Previous collaborations: "Shallow Grave” (1994); "Trainspotting" (1996); “A Life Less Ordinary” (1997)
Why Boyle should: Well, Boyle’s career is looking rosy enough that he doesn’t particularly need any one actor. Still, while many of his most successful films have had young men at their center, it would be interesting to see him adopt a more mature perspective. Boyle claims he’s still interested in an adaptation of Irvine Welsh’s “Trainspotting” sequel “Porno,” and it’s hard to see how that can happen without McGregor.
Why McGregor should: Okay, so this presents a bit of an obstacle. McGregor fell out acrimoniously with Boyle in 2000, when the director courted him for “The Beach” before handing the role to Leonardo DiCaprio – and the actor refuses to bury the hatchet. But 13 years is a long time, guys. And while McGregor recently registered strongly in “The Impossible” and “Beginners,” he could use another role with the sharper edges of his “Trainspotting” breakthrough. A reunion with Boyle could bring him that.

- Guy Lodge