Anton Lesser (probably most recognisable to today's viewers as Qyburn from GoT) has been the biggest example of this to me. I've seen him in dozens of things over the last four decades, and he is consistently like an entirely different person. A true chameleon. His name popping up in the credits is always a bit of a personal gotcha moment.
I didn't realize that Cole Sprouse who played Will in the 2019 drama film 'Five Feet Apart' in conjunction with his twin brother Dylan played the young boy adopted by Adam Sandler's character Sonny in 'Big Daddy', 20 years earlier in 1999.
While very different films, both 'Big Daddy' and 'Five Feet Apart' have two of the most memorable faux pas committed by characters in movies I have ever seen. In 'Big Daddy', Sonny when seeing his friend start to make a speech yells out across the room, "Are you going to propose?" and his friend was indeed about to propose to his girlfriend. In 'Five Feet Apart', Will has only nice intentions when he addresses the death of his growing love interest Stella's sister a year earlier, but saying in a loud voice, 'I'm sorry to hear that your sister is dead' definitely wasn't tactful or sensitive.
Leah Remini was in Cheers when she was younger, as was Lisa Kudrow
There were several more on Cheers, including Marcia Cross, "Captain Janeway", Harry Connick Jr, Thomas Haden Church, Harry Anderson (the main guy in Night Court), Roz from Frasier, Jennifer Tilly, Brenda Strong, Sherilyn Fenn, etc, and Data