Some guy leaning on my car

[Mr 5 0]

KG88GT:

I share your annoyance with thoughtless people that lean on your car as if it was theirs.

Almost all of my friends are 'car guys' so no one would even think about leaning on someone else's car, much less sit in it uninvited.
Unwritten rules and all that.

I'm not sure if the types that lean on other people's cars are simply thoughtless or just acting macho; probably depends on the situation but I believe a lot of the 'thoughtlessness' stems from a lack of respect for others to begin with and also a lack of understanding about how owners of nice cars feel about them.

In any case, I like how you handled it. Plainly annoyed but not hostile or looking to make it out to be more than it was. No harm done; good example for your son, too.