No – it’s not rotten. In fact, it’s completely fresh in the sense that “Something Rotten!” is an original musical comedy that is receiving its world premiere on Broadway, without a regional tryout or Off-Broadway run.

Four years ago, “The Book of Mormon” also opened fresh on Broadway, but everybody knew the creators of “South Park” had something special on their hands. On the other hand, “Something Rotten!” was written by unknowns, though Casey Nicholaw (“The Book of Mormon,” “Aladdin”) is the director-choreographer.

You could describe “Something Rotten!” as “Shakespeare in Love” meets “Spamalot.” Set in Elizabethan England, a struggling playwright (Brian d’Arcy James), unable to compete with the ever-popular Shakespeare (Christian Borle), visits a soothsayer (Brad Oscar) to find out what’s going to be the next hot trend in the theater: “Musicals!” he is told.

He then asks what Shakespeare’s biggest hit will be, hoping to rip off the Bard. Instead of “Hamlet,” the soothsayer says “omelette,” so a breakfast-themed musical is prepared, chock full of nods to classic musicals.

All the while, the playwright’s earnest brother (John Cariani) writes what actually is “Hamlet,” while a prying Shakespeare takes notes.

With all its showmanship and silliness, “Something Rotten!” begins on an extremely promising note, sustains it throughout act one, and then falters in act two, where attempts are made to resolve the haywire plot. Perhaps a tryout run was needed to work out the kinks.

Even so, “Something Rotten!” is a great deal of cartoonish fun, especially for musical theater fans who can appreciate the inside references, which range from the megahit “Cats” to the flop “Chess.” Its cheery songs are enjoyable and hummable (the tune of “Welcome to the Renaissance” will stay in your head for days).

The cast is comprised of musical theater veterans who deliver larger-than-life performances. Borle is especially hilarious, portraying Shakespeare like a narcissistic rock star, and James gives a sympathetic turn in the leading role.

If you go: “Something Rotten!” plays an open run at the St. James Theatre. 246 W. 44th St., RottenBroadway.com.