I think the movie title was (it just came to me and I've not googled to confirm) McCabe and Mrs. Miller. Might have been directed by Mike Nichols, who might have also directed The Graduate.
And still, it might be Katharine Ross and not Julie Harris. The google will know, but jr is not about to get distracted by factoids, as he is on a short break from workywork and must get back to his desk soon.
"Plastics":
It's the famous punchline from The Graduate, where poor old clueless Dustin Hoffman has no idea what he wants to do after college, and one of his parents' friends pulls him aside (was the puller-asider the husband of the Anne Bancroft character? Mrs. Robinson in the movie? kuku-cachoo?, who is the mother of Elaine?, that same Elaine who The Graduate wisks away from the altar in the scene you posted, venuscat?)
So, earlier in the movie, the guy pulls The Graduate aside, and says with dramatic effect to him, that the key to his successful future will be, drumroll please:
"I got one word for you, Benjamin:
Plastics!"
Hi-jinks and hilarity ensue. I wonder if it's on Netflix.