I remember an old cartoon, but I cannot find it. I saw it in the 90s on Cartoon Network, but the animation was older.
It was like Scooby Doo, but male protagonist was something like werewolf - if he's shown a picture of the moon, he turns into a wolf and when "they" show him a picture of the Sun, he turns back into human. It wasn't the Scooby Doo movie - that I know for sure.