"Britney Spears episode" is gracing the top of Twitter's most talked about topics on September 29 at 7:30 AM GMT.

The singer appeared on American TV show Glee. Twitter users are using their 140 characters to talk about her performance as "Heather Morris" (a term that is also trending in third place on the chart) on the hit musical/drama series.

"Only Exception," a song by American band Paramore that was featured in the most recent episode of Glee, is also in the charts in eighth place.  

International launch dates for Nintendo's much anticipated 3D portable game console, the "Nintendo 3DS," have been announced along with pricing information and details about new games for the glasses-free 3D console.

The term has shot into second place as microbloggers tweet, "Nintendo's Iwata announces the #3DS will launch in Japan on Feb 26 and will cost 25,000 yen. US and Europe in March" and "Nintendo 3DS out around Feb 26th! I will get it day one!"

"#flagontheplay," "#newtwitter" and "#29s" are trending in fourth, fifth and sixth place in the charts while "Goedemorgen," the Dutch word for "good morning" remains unchanged in ninth place.

Research In Motion's BlackBerry "PlayBook" tablet is in seventh place and "Members Project" (a term promoted by American Express) takes tenth place on Twitter's trending topics list.

The top 10 most talked about topics on Twitter on September 29 at 7:30 AM GMT are:

  1. Britney Spears episode (new)
  2. Nintendo 3DS (new)
  3. Heather Morris (new)
  4. #flagontheplay (new)
  5. #newtwitter (re-entry)
  6. #29s (new)
  7. PlayBook (new)
  8. Only Exception (new)
  9. Goedemorgen (unchanged)
  10. Members Project (promoted)