The hunt is on: Mark Ruffalo, who plays Bruce Banner -- the Hulk in the Marvel Cinematic Universe --  has left his backpack in a New York taxi. To plead for help he took to Twitter, posting a picture of a similar bag and saying, "New Yorkers that I love so much, please help me find my backpack... I left my black w/ red trim Topo backpack in a yellow cab tonight (looks like the one in the pic) in UWS of NYC with no way to contact the cab & don’t know the #."RELATED: Marvel India Trolls Fans Awaiting Avengers 4 TrailerSome fans responded with helpful suggestions. Some referenced an incident when Ruffalo had lost his wallet. Some had cheeky jokes about finding the backpack in the Hulk's giant purple pants. Others, however, have only one thing on their minds: Does this have anything to do with Avengers 4? 

"'Avengers 4 Teaser May be released soon'......" reads one comment, accompanied by a gif expressing suspicion. Another says outright, "I guarantee this backpack contained a rough cut of Avengers 4."

Ruffalo's search for his property, however, turned out to be successful thanks to his communications with the NYC Taxi & Limousine Commission, so it's unlikely that there was any kind of Marvel movie promotion involved.

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The world may never know what was in the backpack, but Ruffalo will no doubt be relieved to have it back. And regardless of when and how the trailer for Avengers 4 is revealed, Ruffalo himself will be there in the movie when it's released on May 3, 2019.