Extraneous Spidey references.
There's at least a couple times, that I remember, when some "random" graphitti in a scene says something like "Hey Spidey!" Plus I think they quote the "with great power comes great responsibility" line at least once as well. Considering how much the character looks and acts like Spider-man, this can't be an accident. Anyone else notice these or others (especially if you've seen the movie more than once, which I haven't)?
"Frustration is the handmaiden of creativity." -Chuck Jones