“Spamalot” follows the travails of King Arthur as he gathers knights to join him on his quest for the Holy Grail. Suddenly the men realize that where they belong is on Broadway.

Turning the 1974 classic comedy “Monty Python and the Holy Grail” into “Spamalot” took Python member Eric Idle three years of work. And it looks like that hard work is paying off, with the show proving a critical darling in its pre-Broadway run and a box-office smash before it even opens.

The current Broadway season has seen several new musicals disappoint, including “Good Vibrations” and “Brooklyn.” Both are hovering near 60 percent capacity at their theaters.

But “Spamalot,” which is scheduled to open on the Great White Way on Thursday, could be the savior. The show has been filling more than 90 percent of the seats at the Shubert Theater in previews and taking a weekly gross of more than $750,000, rivaling such smash hits as “The Lion King,” “Wicked” and “Mamma Mia!” And advance ticket sales have been spectacular, approaching $18 million.

Along with the Python draw, the musical features a top-notch cast of stellar comedians led by Tim Curry, best known for his cult role in garters and black leather in “The Rocky Horror Picture Show,” as King Arthur.

Emmy winners Hank Azaria (“The Simpsons”) and David Hyde-Pierce, coming off his 11-year run as Dr. Niles Crane on the NBC sitcom “Frasier,” take on multiple roles in the show. Sara Ramirez plays The Lady of the Lake.