Me: Hey! Stop it! Don't barge [Pupil A] into the wall!
[Pupil A, but another A*]: But sir! She said I was a bi-polar bear!
I immediately thought that that is one hell of a migration for something the size of a bear, and wouldn't that kind of long distance movement be highly visible?
My second thought was clearly that this was a bear which swings both ways.
Finally this is a bear which is sometimes Grizzly.
The internet has some other answers.
* It's confusing, but there were two pupils whose names began with A were involved in this incident.