Continuity mistake: In the scene in the kitchen with Val, Fran takes two green cups and places them on the bench. She takes two teabags and places them in the cups. In the next scene the two cups are on the table with Val, and Fran carries the teabags over to them and puts them in.
Other mistake: Pretending to be Max's assistant, Fran dials a number for Bernadette Peters. The conversation is on speaker phone. The assistant says "one moment please." Niles and Fran continue talking and Maxwell comes in. Fran and Niles sheepishly hurry out of the room. Notice how, this whole time, Fran never touched the phone again to turn the phone off. So Max would hear Bernadette Peters and actually figure out Niles and Fran's plan before the episode's even halfway over.