"Its Always Sunny in Philadelphia MAC System T Shirt The Mac System, which seems to work very well for Mac when chasing after the ladies! In an episode of It's Always Sunny in Philadelphia, Dennis explains his ""Dennis System"" and attempts to hook up with a girl with some success. However, when Dennis' lie is revealed, Mac stoops in and takes the lady away using what he calls the Mac System - ""Move in after Completion"". This fun black t-shirt is decorated with Mac's image with this famous quote that was used in the episode. You'll complete your own moves with the Mac System when wearing this t-shirt out!".