A park slide + cute Little Mister = Bad hair day
The Science behind the play:
If two things have different charges, they attract, or pull towards each other. If two things have the same charge, they repel, or push away from each other.
So, sliding on the slide caused a positive charge to be built up on each hair. Since each hair has the same charge, they all try to push away from each other and end up standing up straight.