Visible crew/equipment: In the episode "Hotel Inspector," when London comes to tell Maddie about something, she says, "Dogs playing poker," and you can see studio lights on her sunglasses.
Visible crew/equipment: In the episode "Hotel Inspector", when the man with glasses comes in, you can see a light on his glasses that looks like a studio light. (00:18:30)
Answer: Keep in mind, Muriel wasn't very popular. So the writers/directors must have thought it'd be a good idea to let go of the character. No one seems to be complaining.