i don't see how Modine and Moore inviting Ward and Archer round to a party fit in with the themes of the film. and what's with the clown make-up and \modine's weird scream? it feels heavily symbolic but i don't know how.
shareUh, the party scene was a plot point that allowed both of those couples, each dealing with their brand of relationship problems, to bury them as though they didn't exist and meet up to have a good ol' time. There's been some infidelity on one side, there's been some incredibly selfish, disgusting behaviour on the other, but life goes on and these people just play along.
The party was, of course, the reason Modine's character pressed Moore's until she hysterically exploded and eventually divulged the truth about her sexual escapade.
As for the use of Claire's clown make-up... well, they were pretty drunk so it was meant to be just another silly little game. Same goes for Modine's inspired scream.
Clear eyes, full hearts, can't lose.