Go watch Son of Frankenstein, the movie that Young Frankenstein draws most of its material from. In that movie, the titular son of Frankenstein has a son of his own; a young boy who bears more than a passing resemblance to Gene Wilder, who plays the grandson of Victor Frankenstein. Coincidence, or perfect casting?
If you were to read a script of the Monster's last scene with Elizabeth, all of his dialogue could be very accurately transcribed as "Grunt", and he still manages to come across as intelligent and sophisticated.
Another Genius Bonus: In every other version of the story, Frankenstein is repulsed by his creation and rejects it, causing said creation to act out and cause mayhem, becoming a poster child for Creating Life Is Bad along with a Deconstruction of what creating a new life entailed. But in the Affectionate Parody, that trope gets turned on its ear. Frankenstein comes to a Heel Realization and realizes that this "monster" is his child, and a child he has to care for. Because he does what no other version was willing to do and take responsibility, which Reconstructs the whole idea, the film has a happy ending where both Frankenstein and his creation come out benefiting one another.
Another Genius Bonus: in the original book, Frankenstein, Frankenstein is intentionally vague on how he created the monster because he doesn't want anyone else to learn how to do it. Hence the fact that Frederick finds the notes on how to do it in a separate book, titled "How I Did It."
A small propmaking detail closes a plot hole from the original Frankenstein film. In the original, the brain jars have their labels on the covers and Fritz grabs the whole abnormal brain jar after breaking the normal one, leaving it questionable how the brain could make it into the Monster with Fritz delivering Frankenstein a jar that's labeled with a good reason it shouldn't be used—either Fritz would notice the problem or Henry definitely would when the word "Abnormal" is staring either of them in the face at the laboratory. In Young Frankenstein, this is solved— the labels are on the bases of cloches and the jars are separate pieces resting inside the cloches, so Igor takes the unlabeled abnormal brain's jar out of the labeled cloche to Frederick, making the uncaught nature of the error much more believable. Furthermore, since Igor may have been aware of his mistake during the interrogation, he was able to pass it off so far by not giving Frederick a label with the faulty brain.
