Okay, need some help here.
When you talk to this professor, he gives you a Larvitar and a Pokedex. When the player opens the main menu and goes to any sub-menu that covers the whole screen, (e.g. Pokemon menu, Bag menu, Trainer card etc.) and closes the main menu, the player controls the professor instead of his/her own sprite.
When the menu is opened again, and the player opens the sub-menus and closes the menu again, the professor sprite changes into the male character sprite (Sprite 0)
By the way, it also happens with the other guy (the assistant) in the lab.
Here's my script:
And here's the screenshot.