Scary German Guy, played by Leonardo Cimono, is a fictional character who was featured in the 1987 film The Monster Squad.
Scary German Guy, as members of The Monster Squad refer to him, is an elderly man with a German accent who, by his looks alone, frighten the squad members. When Sean Crenshaw is gifted Abraham Van Helsing's diary, he finds that it's written in German.
He, Patrick Rhodes, and Horace go to his home to ask him to translate it for them. As it turns out, not only does he translate it, but he is quite friendly. As they leave his home they commend him for his knowledge of monsters and the scene focuses on his concentration camp tattoo, confirming he is fully aware the world has monsters.
When The Monster Squad has prepared to take on the monsters in town, they rely on Scary German Guy and Phoebe Crenshaw to read the texts from the diary which opens a portal that pulls the monsters into it.