Visible crew/equipment: When Mrs. Doubtfire is cooking in the kitchen, sets her fake breasts on fire, then hits them with the pan lids to put them out, you can see the camera crew in the reflection of one of the pan lids.
Visible crew/equipment: In the scene where Mrs. Doubtfire and the kids are on a trolley, as the trolley passes you can see the crew in the trolley window.
Visible crew/equipment: When Daniel is having a spaghetti dinner with Chris, Lydia and Natalie in his flat, you can see the equipment crew reflected in the picture frame before we see the family eating.
Answer: Daniel was pretending to be different people that were just all very horrible, so he used different accents. This way, when the "British nanny" calls, he was hoping Miranda would instantly consider him. If he called pretending to be Ms. Doubtfire right away, she might not have basically given him the job right away. And if he used the charming British accent for all his characters, it would have lost its charm when he decided to be Ms. Doubtfire.
Bishop73
Basically this. He wanted Miranda to be frustrated by the other calls, so that Mrs. Doubtfire would seem like a refreshing change.
Azalea