Since it’s become clear that everyone leaves D.C. in August, tonight’s Screen on the Green, the last of the season, shouldn’t require arriving three hours early for a decent patch of grass on which to do the HBO dance.

The weather’s perfect and it’s one of the good ones, folks: Casablanca. And did you know this? The 1942 movie’s “special effects” included a miniature cardboard cutout of a plane on a sound stage, made to look real and full-size with the help of a crew of little people getting it ready for takeoff. Ridley Scott thought it was a such brilliant and low-cost move, he used it in 1979’s Alien, dressing up his kid and his friends in spacesuits. Go tonight and see if you can tell which extras are not quite full-size!

WHEN: 8ish

WHERE: On the Mall, off Constitution, between 4th and 7th Streets

BRING: Friends, family, a blanket, snacks, a cell phone (because no one can remember how we found each other in a crowd pre-1993)

DON’T BRING: Dogs, cats, booze (unless you put it on a Thermos), tall chairs (unless you want someone to throw a Thermos full of booze at that back of your head)