Universal did not "buy" the rights to "Frankenstein"--the novel had long since been in the public domain.
NB - While the above note is correct, in April 1931 Universal did buy the film production rights to the 1927 PLAY of Frankenstein by Peggy Webling and this was a key source of inspiration for the film released later that year. In the documentary this was originally elaborated on at some length, including Hamilton Deane's connection to the role - but the need to shorten the running time to a workable length led to the removal of most of the sequence - hence a mistake by omission.
NB - While the above note is correct, in April 1931 Universal did buy the film production rights to the 1927 PLAY of Frankenstein by Peggy Webling and this was a key source of inspiration for the film released later that year. In the documentary this was originally elaborated on at some length, including Hamilton Deane's connection to the role - but the need to shorten the running time to a workable length led to the removal of most of the sequence - hence a mistake by omission.
An interviewee says that Karloff had a run-of-show contract for "Arsenic and Old Lace," implying he was with the show for the full 3 1/2 years. In fact, he was in it for about 17 months.
When the interviewee is speaking about the photograph of Boris Karloff with his three brothers, he says Karloff is on the left. Karloff is on the right of the photo.