It's Always Sunny In Philadelphia: 10 Times Dennis Reynolds Embraced His Inner Sociopath

Charlie's obsession with The Waitress has caused a lot of friction within the group and has at times, thrown off the dynamic the gang shares. When Charlie learns that Frank has slept with her, tears well in his eyes and his heartbreak is visible.

When Dennis sleeps with her, Charlie makes the decision that Mac is his best friend. A decision that does not sit well with Dennis. It becomes clear that Dennis doesn't really care if Charlie considers him as his best friend, he just doesn't want Mac having that title.

His narcissism gets the better of him and he engages in a twisted game of manipulation, toying with Charlie and Mac's feelings and pitting the two against each other in a bid to come out on top. He handles the situation masterfully and plays the situation like a bona fide virtuoso, as if his closest friends' feelings mean nothing to him.

It's also revealed that Dennis has a video collection to rival Blockbuster, and secretly records all his sexual encounters and gives them star ratings so he can enjoy at a later date, in true Patrick Bateman fashion. Throughout the episode he demonstrates a clear lack of empathy and an inability to consider anyone's feelings but his own, and the cracks in the facade continue to grow.