Those guys certainly have a knack for creating cute and endearing characters from the most unusual sources. Heck, if they can make a rat endearing in Ratatouille they can make anything cute. :-) For me, the little guy in the poster evokes images of E.T., and he does share the "all alone" aspect of that character in the film as well.
Unfortunately we've got a pretty long wait for Wall-E... it doesn't open until June 27th, 2008.
Source: IGN via JoBlo