This week’s award for Strangest Thing Seen in Cam­bridge is a tie between two strong contenders:

1. The man rid­ing a uni­cy­cle across the Longfel­low Bridge while push­ing a double-wide baby stroller and hum­ming an uniden­ti­fi­able tune on Mon­day, and
2. The guy dri­ving through Har­vard Square on Thurs­day with a mat­tress lashed to the roof of his car, who was shout­ing, “Some­one help! There’s a bed on top of my car!” at ran­dom pedestrians.