One of the stars billed in the movie is the legendary Bela Legosi. However, he died shortly after filming began and director Ed Wood went in search of a replacement. He chose his wife's chiropractor, a man that looked nothing like Bela. Ed decided to just have the replacement walk around with his cape up over his face, hoping no one would notice the drastic change.
This would be classified as trivia. It would not be considered a goof, since it was done intentionally, and there was no attempt to pretend otherwise. The VHS release even goes so far to say "Almost starring Bela Lugosi".