There are three juxtapositions in the party scenes in I and II.

First is in I Sonny has to be restrained after he spits near the FBI guy taking down license plates, while in II they are
serving treats to the State Troopers who are acting as guards.

Second shows that Clemenza and Frankie were cut of the same cloth. Clemenza quenches his thirst by taking a swig of wine from a pitcher while Frankie quenches his thirst from a hose.

Third, in I Fredo is totally wasted when he meets Kay, and Michael is amused. In II Fredo's wife is totally wasted and Michael is NOT amused.