This is happening down by Museu Nacional d'Art Catalunya. People are walking in and around the surrounding park areas and feel a splat on their heads/shoulders/back. They look and see what looks like bird shit. A couple then come over and 'help' clean it off. The only thing they are helping themselves to is your belongings - pick pocketing to their hearts content. They are squirting fake bird shit and cleaning people out - be warned.
That's all the scams I have for now....