For the past year or so, I've been seeing these little men/robots all over downtown. They come in a variety of colors - I've seen white, yellow and red. This one is in the crosswalk at Wells and Wacker.
I did a little searching and found some info from Chicago Time Out Magazine:
"The person responsible is stikman, a mysterious guerilla artist from Philadelphia who’s a sort of art-world Johnny Appleseed: His trademark robot paste-ups have been spotted in several big cities, from New York City to L.A. The figures started appearing on downtown pavement here (crosswalks along Michigan Avenue are a hot spot) in the middle of the summer . Perhaps stikman did some work while in town for Lollapalooza? It’s difficult to say because we weren’t able to contact the artist directly. The only journalist to speak with stikman was the Washington Post’s Stephen Lowman, who, after a telephone interview in September 2008, wrote that the artist was “soft-spoken and thoughtful.” The only clue to stikman’s identity wasn’t much of a lead at all: He asked to be called Bob."