Simple visual effects are sometimes the most effective

This video really inspires me when it comes to simple, yet effective visual effects. The only real effects used are the large heads of the band members, but for weeks now I have been wondering how they have done it.

At first I thought it might of simply been enlarging the heads of the characters, but then I noticed things like shadows and lighting don't 100% match their surroundings, although it is well done. Also, there is no masking that would make the edge of their faces bleed out and show some background (Also, that would be a monster of a job frame-by-fram masking them.) So my other thought into it was they green screened the actors and simply keyed it out. They then might of tracked onto the eyes or had the band members wearing a tracking hat and then plonked the faces on. Either way, it's something I would love to try and do in the future. I have a thing for large headed images, but in video it's not something I have seen too much before. I shall try this at some point I hope! :)