... I've seen this guy in more than four movies.
You might have seen his son, Skeleton (II). /nm11225842
That must be it!
His iMDB page lists only one: House on Haunted Hill (1959). Interestingly, where it lists Family, it says: "Children: Skeleton". (I'm not making this up!)
Haha When they say he's got skeletons in his closet, they're actually just his relatives.
For sure! He was definitely in "The Rocky Horror Picture Show" among others...