Jack Black arrives at the MTV Video Music Awards on Sunday Sept. 13, 2009 in New York. [Agencies]?

NEW YORK – The MTV Video Music Awards are known for kicking off with the kind of zaniness that has come to define the show, from a dazed Britney Spears to a disgraced Pee-wee Herman.

But on Sunday, it is expected to have a somber start with a musical tribute to Michael Jackson, led by his sister Janet. Madonna will introduce the segment with a speech, according to persons familiar with the production of the show who asked that their names not be used because they were not authorized to reveal details of the show.

Jackson died a drug-induced death in Los Angeles on June 25 at age 50. The medical examiner's office has labeled the death a homicide, and prosecutors are still investigating.

Jackson was not only an integral part of MTV's history — his legendary videos changed the way music clips were made and he was the first black artist whose work was aired on the fledgling network — but he also provided the VMAs with some of its most memorable moments, including his infamous smooch with then-wife Lisa Marie Presley, in 1994.

The Jackson tribute won't be the only moment where Jackson's presence will be felt. The network is also airing the premiere of the trailer for "This Is It," the documentary about Jackson's preparations for his comeback concerts that were to be held in London. The film is due to come out in October.

Both the trailer and the tribute are sure to spark some sad emotions, but with a show to be hosted by British comedian Russell Brand and featuring acts ranging from Lady Gaga to Pink, those bittersweet moments won't last for long. Last year, Brand made his debut as host by poking fun at the Jonas Brothers' vow of purity, among other ribald moments.

There were plenty of colorful moments before the show began, as celebrities including Pink and Buzz Aldrin mingled in front of the cameras at Radio City Music Hall.

Lady Gaga made one of the more intriguing entrances, wearing a top hat, a gold mask looking like something out of "Phantom of the Opera" and feathered bodice. She also had some intimate moments with a celebrity date even more famous — Kermit the Frog. They kissed several times, leading Kermit to openly worry about the reaction from longtime galpal Miss Piggy.

Not to be outdone, teen sensation Taylor Swift arrived in a fairy-tale carriage driven by white horses.

Beyonce and Lady GaGa lead all artists with nine nominations each, but the show's winners aren't nearly as memorable as the wacky and wild moments, and noteworthy performances.

Both superstars are expected to perform, along with Jay-Z, Taylor Swift, Green Day and other acts. And the night won't just focus on music: Robert Pattinson, Kristen Stewart and Taylor Lautner, the much fawned-over stars from the vampire film "Twilight," will present clips from the movie's sequel, "New Moon."