Here's how Mac's mother Mrs. McDonald has (slightly) evolved over the years in It's Always Sunny In Philadelphia. Despite centering around five generally despicable human beings with almost no redeemable qualities, It's Always Sunny In Philadelphia has lasted for fifteen years and counting. Debuting on FX back in 2005, It's Always Sunny In Philadelphia revolves around the antics of "The Gang" from dive bar Paddy's Pub. Mac, Dennis, Dee, Frank and Charlie often find themselves caught up in weird schemes that almost always go wrong - often through their own stupidity or inability to act like rational people.
It's Always Sunny In Philadelphia is the dark alternative to more colorful sitcom fare like The Big Bang Theory, which has clearly struck a chord with viewers. This is largely down to the chemistry of the cast, and it always makes clear that joke is on the gang. The series was renewed for season 15 in May 2020, continuing its streak as one of the longest-running live-action sitcoms in television history.
One thing to note about It's Always Sunny In Philadelphia's main characters is that they've barely evolved over the course of fifteen years. They essentially stuck in the same cycles and routines, and seem doomed to live out life without growing in any meaningful way. That said, after years of denying the obvious truth to himself and everyone else, Mac finally came out as gay during season 11. Mac shares a famously strained relationship with his convict father Luther and his mother (Sandy Martin), whose first name has never been revealed.
Mrs. McDonald is delightfully gruff and monosyllabic and has spent a good deal of her screentime on It's Always Sunny In Philadelphia smoking and watching TV. When Mac or the gang comes to visit she barely acknowledges them, and it's up to her son to translate her grunts to the others. Like most of the characters on the show Mac's mom has barely changed, though she's at least formed something of a friendship. During season 6 she's forced to move in with Charlie's mother Bonnie for a truly odd couple pairing.
They don't get off to a good start, with Mac's mom attacking Bonnie if she tries to wake her from a nap, but they're still living together, and in season 12's "Old Lady House: A Situation Comedy" the gang tries to make a sitcom from their pairing. The fact Mrs. McDonald seems to have formed any kind of relationship on It's Always Sunny In Philadelphia is a move in the right direction for her personal growth - even if it's likely just borne out of convenience.