Mark Ruffalo had lost wallet returned by stranger through Twitter

The good Samaritan tweeted to the star: "I have your wallet. Found it in a cab in Chicago on Friday. Let me know the best way to get it back to you. Thanks."

It took a couple of days for the actor to see the message, but he could barely contain his gratitude when he did respond.

He said: "Thank you! Wow! Another point for the decency in people."

The pair then reportedly exchanged a few direct messages on the social networking website to arrange the safe return of the wallet.

The 'Begin Again' actor later concluded: "You are a hero!"

Meanwhile, Mark recently expressed an interest in appearing in a Hulk solo movie, and he thinks it would be particularly fascinating to explore the conflict between his character Bruce Banner and his superhero alter ego.

He said recently: "It could get very boring to watch the guy who's moping around who doesn't want to do the very thing that we're all dying to see him do.

"And so I think that's the tough part of cracking that nut. I think that's what's made it problematical in the past. But I do feel like we've gained some ground on this new version of him, which has - he's sort of turning to face himself, and I think the relationship between Banner and The Hulk as a conscious conflict, it could be really interesting."