A few months back (a lifetime in blog-years) A Continuous Lean posted Could This Be The Preppiest Movie Ever, citing the modern classic Trading Places. Cracking. I have a stealth pick though for the everyman preppy; Splash. Hear me out...
Morning suit on the beach in Cape Cod (sidenote; landcruiser? and hey... like the moron twin's maroon rugby), golden fleece at the raquetball club, OCBD's with windbreaker/cord jacket/letterman, then for dinner it is blue blazer and grey flannels. Not bad Mr. Alan Bauer.
Sidenote: this was the first vhs movie we owned (second was Trading Places I think) back when a 'remote' for your vcr was a 6foot cable. I think I can repeat the whole movie verbatum...