Troyer recently starred in The Love Guru, reuniting him with Mike Myers
Celebrity Big Brother's return has proved a hit with viewers with more than 5.5 million tuning in to watch.
It drew in 5.9 million at its peak, beating BBC One's Morecambe and Wise: The Show What Paul Merton did (3.9) and ITV1's Midsomer Murders (5.3).
But it was still down on the 7.3 million who watched Channel 4's 2007 launch, and before a racism row led to 2008's series being cancelled.
La Toya Jackson and TV host Ulrika Jonsson are among those taking part.
Austin Powers actor Verne Troyer, singer Mutya Buena, presenter Terry Christian and Shameless actress Tina Malone are also in the line-up.
Singers Ben Adams and Michelle Heaton, US rapper Coolio, Scottish politician Tommy Sheridan and glamour model Lucy Pinder complete the household.
Channel 4's David Williams, commissioning editor for Big Brother, said: "CBB is back with a bang. After all the speculation in the press about the line-up it was worth seeing them walk through those doors."
In 2007, the series was rocked by a racism row when remarks by Jade Goody to actress Shilpa Shetty drew 54,000 complaints.
House leader Terry Christian will be immune from the public vote
It meant 2008's series was replaced with Big Brother: Celebrity Hijack.
The show saw stars act as Big Brother to a house of "unknowns".
The launch show began on Channel 4 before switching to E4 where the rest of the series was shown.
The 2009 series will run for 22 days, with the first eviction expected to take place next Friday.
In the first twist to the new series, presenter Davina McCall announced for the first time in the show's history, a leader of the celebrity house would be appointed.
Former Word host Christian has been chosen to live in luxurious quarters and will nominate fellow celebrities to face the first public vote.
The 48-year-old will be immune from potential eviction.
The show's executive producer, Sharon Powers, said all of this year's housemates had been reminded about the earlier controversy.
They were also sent DVDs of previous Big Brother series, she added.
Ms Powers said this year's show would "explore the world of celebrity".
"What we aim to do is get an interesting bunch of famous people who we talk to and meet on an individual basis."
Bookmakers Ladbrokes said Troyer, Coolio and former boyband star Ben Adams are currently favourites to win the series.
The Hollywood actor Troyer, who stands at 2ft 8in (83cm) tall, was shown a placard from the crowd which said "Mini Me, will you marry me?"
Bollywood actress Shetty won two years ago, earning 63% of the public vote.