8. SwitchGere - Pretty Woman
Not really a "mistake" as much as it is a horrifying and misjudged attempt to de-age its leading man, the theatrical release poster for
Pretty Woman decided that Richard Gere should have brown hair instead of grey hair, because God forbid the man was getting older and could keep his dignity. So anybody who went to see this rom-com feeling totally pumped about seeing Richard's sleek brown hair probably ended up feeling massively betrayed and disappointed, and was presumably escorted into the street whilst defiantly yelling:
"But they told me it'd be brown!"