A few hours before I was set to interview Breton Sound frontman Jonathan Pretus, I happened to run into him on a Facebook thread. Nothing unusual there, except that it was a thread discussing the Monkees—specifically the discovery of some long-lost Monkee footage, including an alternate ending for their cult-classic movie Head. That’s pure trivia for 99 percent of people in the world, but pure gold for a handful of pop obsessives. Pretus is a proud member of the latter group.

You don’t hav...