Peculiar items are popping up at the home of Cathy and Mark Schroeckenstein, a young couple in Minneapolis.

A cement bunny appeared on the doorstep. A rusted baker’s rack materialized on the patio. A lamp that is “like so gaudy….kind of gold” and “really old school” was plopped in the kitchen, says Ms. Schroeckenstein.

The culprits, it…