It's Always Sunny in Philadelphia Season 8 Episode 6
Charlie's Mom Has Cancer
When Charlie and Mac drop off The Gang's laundry at the apartment shared by their moms, Charlie's mom announces that she has cancer. Charlie then frantically relays the message to the rest of The Gang at Paddy's where Dee is trying to convince Frank he should give her money to see a psychic. Charlie's news barely affects Dennis, prompting him to find a way to find his feelings. Mac proposes going to his mom's doctor who claims he can cure cancer for $4,200. Dee thinks it's a scam, citing old people will fall for anything and using Frank as an example.
Charlie, Mac, and Dennis end up visiting the doctor who goes by "Dr. Jinx" (played by P. Diddy) and uses ancient homeopathic remedies in his office, which happens to be a sketchy garage filled with plants. Charlie and Dennis are still skeptical about his abilities especially after he treats Mac's rash aka 'Sailor's Rot' by spraying it with some green liquid.
Mac proposes going to church where Charlie loses his cool over the scam of kneeling, sitting, standing, and giving money to the church despite their appearance of great wealth. After the service, the priest asks them for more donations because someone broke one of the holy statues, which causes Charlie to lose his cool again. Dennis proposes a 'Beef and Beer and Jesus' at Paddy's to raise money for Dr. Jinx's fee.
Meanwhile, Dee visits her psychic, who tells her and Frank that her deceased mother is actually still alive and hiding money around town.
At Paddy's, Artemis applies make-up to Charlie's Mom who's in a bald cap and covered in fake lesions. She's hesitant about giving a very graphic speech to the guests in order to guilt them into donating. Before she goes on stage, Dennis delivers a moving speech about faith and feeling the spirit that will cure cancer. However, he confesses he felt nothing afterwards.
Midway through her speech, Charlie's Mom confesses she doesn't have cancer. We find out Dr. Jinx is just the church gardener and Dee & Dennis' mom really is dead after they dig up her coffin, causing Dennis to finally break down in a fit of real, genuine tears. Frank gloats to The Gang the whole ordeal was a 'grift' that he planned and executed.