When the grandmother stands up from her wheelchair, the footrests are alternately up or down between shots without anyone adjusting them.
When Cliff enters at the very beginning, there is snow on the glass part of the front door that is visible from both sides of the door. When Frasier enters seconds later, there is no snow.
When Frasier is in the bathroom putting on the wig and Sam is waiting in the hall way. You Can clearly see the stage curtain behind Sam.