Otto Holtenwasser is the Murphys' elderly German-Jewish neighbor. The neighborhood children are convinced that he is a Nazi war criminal, though he is, in reality, a Holocaust survivor. Despite this, he remains jovial and chipper. He is voiced by Trevor Devall.
Mr. Holtenwasser is a friendly man who is always kind to children. Most likely due to his accent, however, a rumor has the kids believing he is a Nazi and therefore are scared of him. Despite this, In "The Bleedin' in Sweden," Bill's magnet gets stuck to the numbers on Holtenwasser's house. When he reaches out to try and take it down for him, we can see the serial number tattooed on his arm. Bill thinks it is the number of people he's killed.
In "The Trough" he gives Kevin a ride home. He recounts to him how he's watched Kevin grow up throughout the years, seeing him playing around the neighborhood. He also mentions that he and his wife were the first homeowners in the subdivision. During this, Kevin notices a Star of David hanging from his rearview mirror but mistakes it for a pentagram. For this reason, Kevin (and later Bill) believe he is a Satan worshipper, even despite Frank's more accurate description of him as "a sad old man whose family was butchered in the war."
In "The Liar's Club," Holtenwasser joins Kevin and Frank and the rest of the neighborhood in the Murphy's basement, remarking he shared a basement with fourteen others in his lifetime. Vic likens this to a life of partying before Holtenwasser reflects it was, really, a very quiet life, "most of the time."
- Mr. Holtenwasser drove Sue to the hospital for Maureen's birth when Frank got caught up with other predicaments.
- Despite his cheerful nature, he despises Jimmy Fitzsimmons like everyone else, and was even happy when he overheard Bill and Phillip talking about how they were the ones who got him sent away.