© Getty Images

Woody Harrelson - The actor also believes that 9/11 was fabricated by the US Government. He was even willing to be on a movie called 'September Morn,' but the project never went ahead.

© Getty Images

Robert De Niro - The actor believes that vaccines are 'bad' for children. The Huffington Post reported how De Niro was at a panel in Washington D.C. to discuss this type of medication.

© Getty Images

Whoopi Goldberg - On the show 'The View,' the actress questioned why the US flag was seen waving on the moon landing pictures.

© Getty Images

Paris Jackson - Michael Jackson's daughter told Rolling Stone magazine she believes her dad was murdered.

© Getty Images

Rosie O'Donnell - Rosie told The View that she also believes that there must have been explosives involved in the 9/11 attacks for the Twin Towers to collapse the way they did.

© Getty Images

Willie Nelson - The famous musician also questioned the way the World Trade Center collapsed during the 9/11 attacks. He said on the Alex Jones Show that he's seen buildings in Las Vegas being detonated the same way.

© Getty Images

B.o.B - The rapper truly believes the Earth is flat! Besides mentioning his belief in many interviews, he's also expressed his theory on his Twitter account often.

© Getty Images

Rob Schneider - The actor also believes vaccines can cause autism and other complications to children. He was heavily criticized by comedian John Oliver on his show.

© Getty Images

Kylie Jenner - In 2015, Kylie shared a picture on Twitter about the famous chemtrails theory, which some people believe are toxic.

© Getty Images

Courtney Love - The singer shared her theory regarding what happened to the Malaysia Airlines 370 plane on her Facebook page. Courtney believed she had located the plane in satellite imagery.

© Getty Images

Prince - The late singer spoke often about what he believed was the New World Order and the Illuminati, and how this organization was controlling the US population, in particular black people.

© Getty Images

Kanye West - The rapper thinks the government created the AIDS virus to target the black and gay communities. He mentioned it on his song 'Heard 'Em Say' and reiterated it in an interview with Rolling Stone.

© Getty Images

Spike Lee - Like Kanye West, the director also believes the government created the AIDS virus to exterminate the black population. He said so during a Rolling Stone interview.

© Getty Images

Billy Corgan - The Smashing Pumpkins also believes in chemtrails. He posted a series of tweets in 2010 about that topic.

© Getty Images

Jenny McCarthy - The actress and writer is one of the most well-known advocates against vaccination. It all started when her son was diagnosed with autism at age two, after taking a series of vaccines.

© Getty Images

Charlie Sheen - The actor spent many years questioning the official 9/11 story. In interviews, he's said that the towers' collapse looks like a controlled explosion.

© Getty Images

Martin Sheen - Charlie Sheen's father believes the same, and he told the Huffington Post in 2012 that there are still many unanswered questions regarding 9/11.

© Getty Images

Marion Cotillard - The actress has spoken in several interviews about two conspiracy theories in which she believes: she thinks the real story about 9/11 is being witheld from the public, and she doesn't seem to think the Man ever stepped on the moon.

© Getty Images

Jim Carrey - The actor and comedian doesn't believe vaccines cause autism, but he still thinks they're dangerous because they contain mercury, a neurotoxin that is harmful to children.

© Getty Images

Mark Ruffalo - The actor also has his doubts regarding the 2001 attacks. He took to social media to criticize the 9/11 Commission, demanding the truth and stating that buildings simply don't fall like that if not via detonation.

© Getty Images

Dave Mustain - During one of his shows, the Megadeth lead singer said he believed Barack Obama had orchestrated mass shootings in the US to get the government to approve gun control policies.

© Getty Images

M.I.A. - The rapper told Nylon magazine that she believes it was the CIA who created Facebook and Google to control people and information flux.

© Getty Images

Ted Nugent - The musician believes global warming is a lie and that it has never been fully proved scientifically. He's expressed his opinion in several interviews, and said that is why he supports Donald Trump, who also claimed climate change was a hoax created by the Chinese.

© Getty Images

Terrence Howard -

Terrence Howard's conspiracy theory is a pretty funny one. The actor told Rolling Stone that math is wrong and that 1x1 equals 2 and not 1, because if the square root of 4 is 2, then the square root of 2 has to be 1!

Sources: (Huffpost, Popular Mechanics, Rolling Stone, Vanity Fair, Nylon)

© Getty Images