 If you liked
Suzumiya Haruhi no Yuuutsu
|
 ...then you might like
Rokujouma no Shinryakusha!?
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Main guy hangs out with characters that are all supernatural. Comedic hiijinks and merry misadventures ensue.
In both series, the main character is surrounded by strange beings (Alien being the only one remaining the same between the two, but similar concept.)
The two series share the same basic premise: a bunch of different supernatural entities independently converge on the same objective, and are therefore forced to interact with each other and one ordinary guy who's stuck in the middle. But whereas in one show, that objective is the observation of a singular high school girl, in the other it is control of a tiny (barely 100 square foot) apartment.
The main difference is in tone. Rokujouma is far more energetic, with stronger action and comedy elements, but consequently lacks the emotional impact and mystery of Haruhi.