It's a wonderful premise, who wouldn't love to be an alien wrecking havoc among the humans? Just a shame this game has so little to do with that. Far too much of your time is spent running around collecting brains, not much more entertaining then playing Spyro.
There are a few interesting ways to collect these brains. Mental powers let you fling the humans into walls and such, and what's more fun then making a head explode after a powerful butt probe? These things are fun, the first hundred times. After a point it's more a chore then a pleasure.
The story isn't too horrible, nothing I would pay to see in theaters but if it was on tv I'd watch it during the commercials of another show. All in all it's a mediocre attempt at a shooter. Amusing for the first half hour, only because most of that time is videos. If you rent this one make sure you have something else you really like to play, you'll need something while this gets sent back.