In parts two and three of its retrospective on 2011, Twitter takes a look at the famous faces that signed up for their very own account and the hottest topics and hashtags this past year.

And with a list including Charlie Sheen, the U.S. Secret Service, the Egyptian revolution and McDonald’s McLobster, they’re quite the eclectic bunch.

Who joined Twitter in 2011?

The movie business had a good showing of new accounts this year. James Cameron signed up at the end of January, Billy Crystal in April, Alec Baldwin in May, and Gwyneth Paltrow took the plunge in June.

We also saw government accounts sign up, such as the U.S. Secret Service in May and the U.K. House of Lords in September.

Plus, there was that oddity account, the Bronx Zoo Cobra, which made a splash in March by tweeting on behalf of the escaped cobra slithering around the city.

But the new account with the most impact this year has got to be Charlie Sheen. He made both the new accounts list and the hottest topics list, signing up for Twitter in March and taking top spot as the most-tweeted-about actor in 2011. And, his #tigerblood hashtag was the second-most-tweeted-about hashtag.

Other hot topics for the past year included the hashtag #egypt which was used during the Egyptian revolution, Rebecca Black and her song “Friday”, the passing of Elizabeth Taylor, a heated discussion about which McDonald’s restaurants serve the McLobster, and the movie “Thor”.

You can see a full list of the 2011′s newest accounts here, and its hottest topics here.