The new Broadway musical Young Frankenstein is nothing if not too much. It has to be colossal, larger than life, overwhelming – being a fun little musical is not an option. If it hasn’t knocked you out of your seat, it’s a failure. Or so the hype and expectation would lead you to believe. The preview audience I saw it with was determined to have a great time, and indeed they seemed to get what they wanted.

Actually, this Mel Brooks show – his first since the smash The Producers – does provide a fair amount of fun for a couple of hours, although it begins rather routinely and weakly. The first two numbers, one sung by the townsfolk of Transylvania Heights and the other by Dr. Frederick Frankenstein (Roger Bart) and his medical school students, are mildly enjoyable but far from brilliant – and they come nowhere near the insane hilarity generated by Gene Wilder, at the start of the 1974 film the show is based on, when he stabs himself with a scalpel.

That, in fact, is one of the few gags from Brooks’s movie that isn’t recreated in the musical. As at Spamalot, another Broadway hit based on a beloved 1970s film comedy, the audience anticipates the familiar material, and applauds and laughs at the setups, preparing to go wild over the old jokes before they ever actually happen. This phenomenon is mildly amusing in itself, but spontaneous it ain’t.

There is new material as well, some good, some less so, but the audience’s need to re-experience the movie’s highlights is a bit of a trap, at least for the book (co-written by Brooks and Thomas Meehan). Brooks’s music and lyrics may be uneven, but they are his best opportunity to create something new here. The songs are pleasingly well crafted and, I’m happy to report, appropriately ridiculous.

There are also at least two real star turns that help a great deal. Megan Mullally takes on the fiancée role played by Madeline Kahn in the movie, and from her first entrance she owns the place. She has far too little to do in the first act after her smash opening number, “Please Don’t Touch Me,” but thank God she’s back with more in Act II – just one additional big song, but plenty of chances to show off her ace comedy timing.

When Dr. Frankenstein arrives in Transylvania, he is greeted by the hunchback Igor, the role originated by Marty Feldman. Christopher Fitzgerald makes the part his own, however, and he too has a smash first number, “Together Again,” a duet that also finally allows Bart to let loose. And from here on the plot begins to gain traction as well – for a while.

One of the problems with Young Frankenstein is that it lacks the magical exploding plot mechanics of the first two-thirds or so of The Producers. That show also managed to keep the hilarity and general insanity at a much higher level than Young Frankenstein, despite some great bits, is able to sustain. Here the story builds to the first-act climax of Frederick creating a monster, just like his grandfather. But in the second act, there is less of a plot engine.