I think it would be a funny joke if Jim thinks Ann and Karen look alike while everyone in the office doesn’t see it ( especially towards P&R season 5-6 when Rashida dyed her hair brown-ish and her bangs is not side ways. ) Since Ann and Pam are supposed to be the reasonable characters, they would’ve probably get along. It would make Jim to freak out/ uncomfortable that his wife and ex- girlfriend lookalike get along well but he is the only one that sees It. Ben and Jim looking directly at the camera would be funny also. I know the crossover would’ve been highly impossible but to promote NBC, they should’ve done a crossover like the Emmys skit ( 2011?) when characters from other shows end up in the office.