Use the Mr. Peabody mouse to get your score up. Make sure the sprite is touching Sherman. It is as simple as that. It will tell you when you win. If Sherman disappears from view just wait a second.
Thanks to the "Mr. Peabody and Sherman Show" for inspiration. Plus "Where is Waldo?" for the title idea and finally SonicFan1006579345, for making what gave me the idea,"Wapac Pen".