When American Ballet Theatre returns to the Metropolitan Opera House on Monday night, it will usher in a spring season loaded with special guest artists, important anniversaries, and two farewells (of sorts).

Without a doubt, the most unexpected guest artist will be a part of the opening night gala: Savion Glover. This tap master will present a piece d’occasion on a program that will also show off the ABT roster: Alessandra Ferri and Julio Bocca will dance the pas de deux from Roland Petit’s “Carmen”; Herman Cornejo and Amanda McKerrow will dance “Le Spectre de la Rose,” a wonderful morsel of virtuoso and artistic dancing; Julie Kent and Vladimir Malakhov are slated for the pas de deux from Act II of “Swan Lake.”

But as the season progresses, other guests will be dropping in, too. Carlos Acosta, of the Royal Ballet, is dancing with ABT this season. He’s a vibrant, athletic dancer with crowd-pleasing jumps and turns in his bag of tricks. Classical but muscle-bound, he’s a powerhouse. He’ll be seen as Ali the slave in “Le Corsaire” (June 25 & 30), as well as the lead in “Swan Lake” (July 8). Also in for the season is Diana Vishneva of the Kirov Ballet. A stunning dancer with extraordinary stage presence, she’ll be starring in “Don Quixote” (May 26),”Ballet Imperial” (May 30),”Swan Lake” (July 5 & 9), and “Giselle” (July 12).

The home team will be getting a few laurels, too. This season, Ms. Ferri will celebrate 20 years of dancing with ABT. A celebratory tribute has been scheduled for her July 15 performance of “Giselle.” There are three other noteworthy landmarks coming up this season. Both Jose Manuel Carreno and Vladimir Malakhov are celebrating 10 years at ABT; they joined the company as principals in 1995. Paloma Herrera, too, will celebrate her tenth year as a principal. The all-star Tchaikovsky program on May 30 will celebrate these anniversaries.

In the departures department, Amanda McKerrow will bid farewell to ABT (but not the stage entirely) on July 14. This deeply artistic dancer is moving out to the West Coast to join up with Ballet Pacifica, where fellow ABT principal Ethan Stiefel will be taking over as artistic director. In a

stroke of good timing, she had decided to make this her last ABT season, and then the opportunity to help Mr. Stiefel came along.

Ms. McKerrow will be teaching and setting ballets, but she’s not ready to declare herself done with performing. “It’s impossible to put a stop on it. I’m just shifting my priorities,” she said. “I’ll dance as the opportunities present themselves.”

Ms. McKerrow and her dancing husband, John Gardner, are experts in setting ballets by Antony Tudor. They will continue that work this summer and move out to California in the fall. “I really like teaching Tudor ballets to today’s young dancers,” Ms. McKerrow said, adding that she sees a hunger for the artistry that such ballets require.

As for Ballet Pacifica, Ms. McKerrow is looking forward to working with Mr. Stiefel and helping him create a new era for the small company. “We hope to bring good, exciting dance to Southern California,” she said.

Also cutting back this season is the amiable Julio Bocca, who will dance his last “Don Quixote” on May 25. He has been gradually retiring individual roles; in 2003, he danced his last Romeo in “Romeo and Juliet.”

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For the newcomer, ballet can appear hermetically sealed and totally unrelated to anything except itself. But all that’s needed is the context of history, music, and popular culture. The easiest way to put ballet in that context is with little bites of cocktail-party trivia. Go ahead, impress your friends at intermission.

1. Who was president of the United States when, on the other side of the globe, Marius Petipa’s “Don Quixote” premiered in Moscow? (Hint: The date was December 26, 1869.) Ulysses S. Grant

2. Who wrote “The Corsaire” on which the ballet “Le Corsaire” (1856, then re-choreographed in 1899) is based? Lord Byron, in 1814.

3. Ballets can be full of many happy occasions. What is celebrated in both “Swan Lake” and “Raymonda”? Birthday parties.

4. In “Giselle,” the heartbroken young girl dies and goes to the underworld, where she joins the Wilis. What is a Wili – and is it an acceptable Scrabble word? The Wilis are the souls of jilted girls who die before their weddings. The word is not listed in the Official Scrabble Player’s Dictionary, but “willy” (to willow) is. Other acceptable ballet-related words are “plie,” “pointe,” and “undine” (a female water spirit).

5. Another handy Scrabble word is “sylphid” (a young sylph). What two ballets are titled after these creatures? And which one is ABT dancing this season? Michel Fokine’s 1909 “Les Sylphides” is a plotless ballet set to Chopin – not to be confused with “La Sylphide,” a narrative ballet (by Phillippe Taglioni, then Bournonville), set in Scotland. ABT is dancing the Fokine ballet.

6. In 1911, Diaghilev’s Ballet Russes presented “Petrouchka” by Fokine. Who first danced the role of Petrouchka? What famous choreographer also danced in the ballet? Vaslav Nijinsky was the first Petrouchka. George Balanchine also danced in this ballet. As he wrote in “101 Stories of the Great Ballets: “‘Petrouchka’ is a ballet for which I have some sentimental recollection. In the Diaghilev production, whenever anyone was sick or unable to dance I took his part in the ballet. At one time I thought I had danced almost every male part in the ballet!”

7. Fokine’s “Polovtsian Dances” is a ballet taken from the opera “Prince Igor” by Alexander Borodin (1833-87). What was Borodin’s day job? Borodin was a chemist in St. Petersburg. He wrote several pieces of music, including one unfinished opera, “Prince Igor.” The ballet is set in the encampment of the Polovtsi tribe, which has captured Igor but still like the idea of putting on a show for him.

8. Two musicians completed “Prince Igor” after Borodin’s death. Who were they – and which one also wrote the score for the 1898 Petipa ballet “Raymonda”? Nikolai Rimsky-Korsakov and Alexander Glazunov completed “Prince Igor.” Glazunov also composed the score for “Raymonda.”

9. Of what ballet score did Tchaikovsky write the following: “What charm, what elegance, what richness of melody, rhythm, harmony. I was ashamed. If I had known this music early then, of course, I would not have written [Swan Lake].” “Sylvia,” by Leo Delibes.

10. Which Fokine ballet was so well received that an audience at the Paris Opera once demanded a repetition of the entire ballet? “Le Spectre de la Rose.”