Skyline is an informercial for the special effects technology and animation studio used in the show. The story was written for principal photography to be done as cheaply as possible (almost entirely at the co-director's condo building), saving all the cash for post. But I don't think it's the worst movie ever. If it had switched locales a few times and thrown in a couple of chase sequences, it would have been decent.
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You can take the heart out of the hooker but you can't take the hooker out of the heart. -- Frankenhooker