For years I thought Mickey Rooney (1920-2014) and Mickey Rourke (1952-present) were the same guy. I'd see Mickey Rooney in a movie and be like "Wow, he's looking pretty good for his age," thinking he was a man 32 years his senior and/or dead.
I finally twigged when I eventually saw Iron Man 2 (2009) and was like "How is he doing this?!" and actually looked him up.
When I was a kid I had hard time distinguishing between actor and role. So Kevin from Home Alone had to be that Kevin Costner the actor, right? Right!?
Then Home Alone would have been 3 hours with an epic speech about why this is the final stroke and why he will stand against the burglars beside some hobos from the woods.