I like Tor.com’s explanation best for the giant styrofoam head found floating in the Hudson River last week:

This past Thursday a giant styrofoam head turned up in the Hudson River. Our suspicion is that it fell through from an alternate 2013 timeline where the Roman Empire never fell.

My second favorite explanation: it fell off a Mardi Gras float in New Orleans and made it’s way up the East Coast via the Gulf Stream. I guess that’s more likely.