AFTER MOVING into an apartment together in Chicago last year, artists Lucas Bucholtz, 39, and Alessandra Norman, 28, decided they needed to spice up their lives even more—which was how they found themselves mingling with dozens of prospects in a crowded Logan Square coffee shop one night last week, trying to decide which one to take home. It’s not that they were bored exactly, but “we want to swap for something more unique than what we already have,” said Mr. Bucholtz, who had his eye on a certain fleshy specimen sitting on a nearby ledge.
In...