Strickland: Why even bother, McFly? You haven't got a chance. You're too much like your old man. No McFly ever amounted to anything in the history of Hill Valley.
Nothing like a little quality encouragement from an educator, eh? But right away we get a little insight into the McFly family condition: a history of failure. Ouch. At least Marty doesn't have to worry about the bar being set very high.
Lorraine: I think it's terrible. Girls chasing boys. When I was your age I never chased a boy, or called a boy, or sat in a parked car with a boy.
Lies! In 1955, when Marty asks Lorraine if she wouldn't mind parking for a sec, she tells him that it's not like she's never parked before. So clearly she's got some skeletons she'd rather keep in the closet. Or else she's forgotten they're in there.
Marty: He's a peeping tom.
Speaking of skeletons… your sordid past as a peeping tom is probably one of the ones you'd want to keep hidden from your offspring. Not even Lorraine ever knew that's what George was doing out there in the middle of the street. But don't we all have our little secrets?
Doc: Maybe you were adopted.
Doc is prompted to make this remark because there are generally some pretty clear similarities between a father and son. Not in this case. Not on the surface, anyway. But good to know it's as obvious to an outsider as it is to the son in question.
Marty: Whoa, wait a minute, Doc, are you telling me that my mother has got the hots for me?
That's got to be a tough pill to swallow. Definitely an argument against time travel. Dating and relationships are already complicated enough as it is.
Lorraine: This is all wrong. I don't know what it is, but when I kiss you, it's like I'm kissing my brother.
Okay, this one might be a tad far-fetched. We're not aware of any particular "kissing gene" that gets passed down from one generation to the next. Regardless, Lorraine is clearly on the right track here. Something about it doesn't feel right—that much certainly makes sense. Maybe just a peck on the cheek and then tuck him in for night-nights next time?