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It appears when the museum is under surveillance by a neighbor

It is the building's animation. After seeing this yesterday, I was wondering the same thing.
http://i1303.photobucket.com/albums/ag145/DJDK-ec/5E8837DC-0A66-4988-804C-D8AE15DB688F-2330-00000C63C3180FBA_zps05f9e319.jpg

The building animations seem randomly active in my own town. I don't see a tie to when they are spurred or not. The museum pictured doesn't have an eye over it.

And they don't all activate the same. Sometimes i see the mental hospital sheet but not Sanjays cat or vice-versa; properties i have next to each other.