The film opens with the discovery of Dr. Victor Frankenstein's will in his Transylvanian village. A skeleton, presumably Dr. Frankenstein's, and a man wrestle for the box holding the will. The man wins, takes it to a town meeting where the will is read and calls for the transfer of the property to the dead scientist's grandson, Frederick. Following this scene we meet the grandson, Dr. Frederick Frankenstein (Gene Wilder), a surgeon who is busy instructing medical students in clinical neuroanatomy (comparing the brain to a cauliflower). When asked about his grandfather by a medical student, Freddy, who pronounces the family name "Fron kon steen", declares that Victor was "a cuckoo". The student is relentless in pursuing the family ties, exasperating Freddy, who finally plunges a scalpel into his thigh, a sight gag paying homage to Peter Sellers' stabbing himself with a letter opener in A Shot in the Dark (1964). When the courier from Transylvania arrives, he persuades Freddy to return to his ancestral castle for the execution of the will. A hilarious railroad platform scene in which Freddy bids goodbye to his "beautiful, flat-chested" (as described in the online original etext of the script by Gene Wilder) fiancée, Elizabeth (Madeline Kahn), only highlights the incredibly neurotic natures of the two lovers -- Wilder as a possessed but wacky scientist and Kahn as a narcissistic and apparently remote and shallow woman.

In Transylvania, Freddy and the viewers meet the remainder of the major characters. Inga (Teri Garr), a bosomy and mindless but beautiful and dedicated blonde, escorts him to the castle, where he meets the hunchback Igor, played by the incomparable Marty Feldman, who instructs Freddy, with one of the lines all Young Frankenstein addicts love to quote, to "walk this way", by which he means with a limp and a cane, not directions to anywhere at all. After remarking that the huge castle doors have huge knockers (which they do) -- which Teri Garr winsomely mistakes for a compliment on her equally huge knockers -- Freddy and his entourage enter the castle and meet Frau Blücher (played magnificently by Cloris Leachman), the spinster who keeps the castle, nourishing an undying flame for Freddy's dead grandfather. Soon Freddy and Inga discover, by means of a secret passageway behind a  -- surprise! surprise! -- revolving bookcase wall in Freddy's room, his grandfather's hidden subterranean laboratory (Brooks used the same electrical apparatus as the 1931 Frankenstein film) and scientific journals. With the materials and methods now at hand, Freddy undergoes a spiritual transformation, embracing his forebear's obsession with creating life from dead bodies, rejecting his earlier rejection of Victor's work as "Doo-Doo!".

At this juncture we move into the scientific creation mode and of course meet the Monster, exuberantly portrayed by the talented Peter Boyle. When Igor tries to steal a brain from a neighboring morgue there occurs the infamous mix-up of an "Abnormal" brain (labelled "DO NOT USE THIS BRAIN!") for the intended brain of H. Delbrück ("the finest natural philosopher, internal medicine diagnostician and chemical therapist of this century" and also the author of 17 cookbooks) making at least this viewer wonder if Mel Brooks had in mind a real scientific genius, Max Delbrück, who had received, only 5 years before, a Nobel Prize in Physiology or Medicine in 1969 for his work on bacteriophages.

The predicted spoofs ensue: the actual process of transforming the very large corpse of Peter Boyle into the very large body of the living Monster (with Inga remarking, after Freddy states that for the experiment to be a success, the monster must have enlarged body parts, that he "vould have an enormous schwanzstucker" -- a pseudo-German/Yiddish word that everyone in the audience immediately comprehends); the inclusion of Gene Wilder's rendition of the legendary exclamation, "It's alive!" by Colin Clive in the 1931 Frankenstein; the monster's mercurial disposition; the wildly comic scene with the Monster meeting the Blind Man (Gene Hackman); the Monster's fascination with music and antipathy to fire -- they all give rise to set pieces of Brooks's unique mix of lowbrow comedy with intellectual puns, Yiddish asides and the ubiquitous combination of visual and physical jokes.

After Elizabeth unexpectedly arrives in Transylvania we witness an apparently unlikely, and therefore uproariously believable, liaison with the Monster outside the castle, with Madeline Kahn eventually taking on the classic Marge Simpson type hairdo of Elsa Lanchester in the 1935 Bride of Frankenstein. The last important scene before the ending involves Freddy nostalgically summoning the Monster back to his natal castle for a transference of Freddy's calm brain to the Monster's. The ending, with the Monster a fully acculturated and now sophisticated man about town, and with Freddy and Inga still in love in Transylvania, is a brilliant win-win result for Freddy, Inga, Elizabeth and the Monster, although hardly predictable. Without giving away too much of the denouement, suffice it to say that the movie ends on a high note transforming, as it were, a linguistic pun into a musical one.