Your sentence is mostly good, but we can make it a little clearer and correct the grammar. Here is a better way to say it:
Penguins look smart! They look like they are wearing black tuxedos.
Explanation:
- We say black tuxedos instead of a black tuxedo because there are many penguins, so more than one tuxedo.
- The word look is fine, and it means they seem smart.
So your improved sentence is: Penguins look smart! They look like they are wearing black tuxedos.