Several passwords for Metal Gear on NES contain clever not so hidden profanity. This triggered Nintendo of America to impose taking vowels out of future passwords.
Metal Gear was intended to be a straight shoot em up ripoff of Capcom’s Commando. But the MSX computers had a hard time processing so many enemies on the screen at once, so it morphed into a game with stealth as the main focus.
Outside America and Japan, Contra was called Gryzor.
The European release of Contra saw the human characters turned into robots due to censorship laws about violence in video games.
The Belmonts in Castlevania commonly use a whip as their main weapon. This was inspired by the Indiana Jones movie series.