New animal game

Here's a new game we played in the car today:

Sierra: Ba Ba Ba Ba
Me: Oh, are you thinking of a sheep?
Sierra: shakes her head no
Me: No? Ok, don't think of a sheep. Whatever you do don't think of a sheep.
PAUSE
Me: Are you thinking of a sheep?
Sierra: Grins, shakes her head no
Me: Ok, good. I'm not thinking of a sheep either. DON'T think of a sheep!
PAUSE (add another 3 or 4 reiterations of the above, and then....)
Sierra: Ba Ba Ba Ba Ba

We proceeded to play it off and on for the rest of the day with all different animals. The funniest part was that when there was another person present, like Daddy or Grandma, she had to know--to make absolutely positive-- that they were not thinking of a sheep either! She would only spring her "surprise" when everyone present had profusely expressed their lack of interest in the given animal.