I can best explain what I mean with an example: Kirk Douglas was a prominent, perhaps, even a great actor. Yet, he was an inappropriate choice for the role of Ulysses/Odysseus because that character was described as having massively broad shoulders and being rather muscular, if not huge. True, I enjoyed the film, but-- Likewise Professor Challenger has a similar physique, but Claude Rains is even more mismatched than Douglas, as he is rather small in stature. Challenger was a bear of a man, as I recall. I loved the film, but could not suppress an occasional snicker.