During a 70s brainstorming session for Raiders, Steven Spielberg and George Lucas seriously considered the idea that Indiana Jones' backstory should totally include the time he had sex with a girl who still had most of her baby teeth. Lucas commented that it would be "amusing," to which Spielberg immediately added that it would be even funnier if Marion was this 12 year-old slut who came on to Indy and seduced him!
Of course, the first movie wouldn't actually show Indiana Jones molesting a tween, but the terrifying implication would have still been there.
Other ages were also suggested, but Lucas made it clear that they shouldn't go higher than 16 with the sex, because then "it's not interesting anymore."
"Harrison, you got a minute? I have something interesting to show you."