Supernatural forces swept into town this weekend for Creation Entertainment’s first-ever Boston “Supernatural’’ convention. The stars of The CW fantasy series gathered at the Hyatt Regency Cambridge to mingle with fans, sign autographs, and, in their downtime, check out the local scenery. Actor Richard Speight Jr., who plays the Trickster and the archangel Gabriel on the show, told us he hadn’t spent a lot of time in Boston, but knew enough about the city to head straight to the Union Oyster House with his costar Matt Cohen and convention favorite Jason Manns. “I know it’s touristy, but still. It’s phenomenal,’’ Speight gushed. His timing was impeccable. During dinner, Aerosmith screamer Steven Tyler showed up, and Speight compared the fan reaction in the restaurant to “Beatlemania.’’ The actor, whose other credits include “Thank You for Smoking,’’ “Band of Brothers,’’ and “Jericho,’’ was a tourist again Saturday, having lunch in Harvard Square with “Supernatural’’ leading men Jared Padalecki and Jensen Ackles. The convention ended yesterday.