My Cats Keep Following Me Into The Bathroom

One of my cats does this! Just as my children had outgrown following me to the bathroom or standing outside the door talking the cats decides to take their place. If I close the door she meows and bats her paws under the door frantically. When she comes in she just sits there or wonders around the bathroom.
In my case I just think the cat was worried about me suddenly being alone in there!