Would you believe Katy Perry's backup dancer during her Super Bowl halftime show is still making news now? After Left Shark became a viral hit (for forgetting his dance moves during the performance), the singer's company applied to trademark the costume to stop people from making money from non-licensed designs.
However, the United States Trademark denied Katy's bid. Trademark examiner David Collier said the drawing submitted did not match the actual Left Shark. He explained, "Specifically, the specimen displays the mark as a stylized depiction of a forward leaning shark in nearly a front profile with a portion of a dorsal fin, two pectoral fins and two legs and feet substituted for the caudal fin on the tail. The shark has five gills, a full mouth with teeth and round eyes with eyelids; however, the drawing displays the mark as a stylized depiction of an upright shark in full front profile with no dorsal fin, two full pectoral fins and two legs and feet; the shark has three gills and the sharks mouth appears without teeth; the shark also has oval eyes without eyelids."
So yes, the design is still free to use.