Cordelia flings water from a sports bottle on Angel. In the next shot the water level in the bottle is unchanged.
The champagne Rebecca and Angel are drinking changes from clear to a light amber color between shots.
While at Angel's office Rebecca invites him to come over for a visit "some time." As evidenced in the episode (1.5) where Cordelia moves into her haunted apartment, there is apparently no particular time limit for such an invitation, or even a need to actually have a specific place to invite the vampire to.
The nova that was used was reported as a 1976 but the body style was for a 1968 - 1972 version of the Nova.