Canadian pop singer Justin Bieber made a guest appearance on the season return of American TV series CSI as "Jason McCann." The character's name has since risen to the top of Twitter's most talked about topics on the morning of September 24.

American actor and singer "Eddie Fisher" is in second place in the trending topics after he passed away from hip surgery complications on September 22.

The memes "#sincewerebeinghonest," "#ihatewhenpeople" and "#okimlying" take up third, fourth and fifth places in the charts while "X4???????????1????," (a Japanese promotion for Canon's EOS Kiss X4 camera with a double zoom kit) is in seventh place.

The season premiere of American TV show Grey's Anatomy aired in the US Thursday night and people on Twitter are talking about it with the terms "Greys" and "anatomy."

"Braai," the Afrikaans term for "barbecue" is in eighth place as people celebrate both National Braai Day and South Africa Heritage Day in South Africa.

The name of Iran's President Mahmoud "Ahmadinejad," who was speaking at the United Nations General Assembly in New York on Thursday, is trending in tenth place.

The top 10 most talked about topics on Twitter on September 24 at 7:30 AM GMT are:

  1. Jason McCann (new)
  2. Eddie Fisher (new)
  3. #sincewerebeinghonest (new)
  4. #ihatewhenpeople (-1)
  5. #okimlying (-1)
  6. Greys (new)
  7. X4???????????1????(new)
  8. Braai (new)
  9. Ahmadinejad (new)
  10. Anatomy (new)