This guy is funny as hell.
I think my single favorite always sunny episode is the Serpico one. Charlie (Kelley's) grey-area ability to read, extreme nativity, possible* extreme mental issues, scheming and psychotic behavior only make him more entertaining.
Having said all that, he (Day) is in a new movie with Jason Bateman, Jason Sudeikis**, Jennifer Aniston***, Colin Farrell****, Kevin Spacey called Horrible Bosses... I won't ruin it for you, click the video (or link if you're on a phone) below.
Source -> http://youtu.be/EDUpOXfwQUo
**ehhh, kind of annoys me but still I get why he exists
***crazy yes, but I truly believe still below the hit/crazy scale line
****I really want to not like, but I feel like he'd be fun to go drinking with...once.