Twitter says it has more than 100 million active users -- a pretty impressive chunk of the online population who are, if nothing else, checking in to see what other people are sharing.

With that many folks on the six-year-old microblogging site, Twitter is always good for a few surprises.

Sure, you already know about such famous tweeters as Ashton Kutcher, Lady Gaga and Shaq. But did you expect funnyman Danny DeVito to create a photo series of his foot in interesting places?

And, sure, Democratic political strategist David Axelrod uses the site to share talking points and links. But who would have expected him to post a candid picture of President Barack Obama with "First Dog" Bo, then turn it into a not-so-subtle jab at GOP front-runner Mitt Romney?

And then, there are the Twitterers who surprise you by being there in the first place.

Whether because of their age, image or interests, some people just don't seem like likely fans of Twitter's 140-character bursts of wit and wisdom (or ... you know ... other stuff). And yet there they are, tweeting to thousands, if not millions, of followers.

Here are 10 well-known people whose Twitter accounts caused us to do a double-take. Let us know in the comments if you think we missed somebody good.

Rupert Murdoch

First, he's 80 years old. Second, he was fresh off of a brutal few months, during which the flagship paper of his media empire folded in shame after a phone-tapping scandal. But that didn't stop the media-empire tycoon from leaping with both feet into the Twitter pool last month.

There have been a few gaffes (chatting with a fake Google co-founder Larry Page, and not seeming to realize that an account set up in his own wife's name was not real) but Murdoch is active on the site and appears in for the long haul.

Sample tweet: @rupertmurdoch Facebook a brilliant achievement, but $75-100bn? Would make Apple look really cheap.

Mark Zuckerberg

If you're the creator of the world's biggest social networking site, it might be surprising that you'd pop up on another.

But there he is. (It's worth noting that Zuck also has an account on upstart Google+ and, for a while, was its most-followed member).

That said, Zuckerberg can't exactly be accused of lighting his Twitter feed afire. He hadn't tweeted since 2009 before January, when he posted a message opposing the now-shelved Stop Online Piracy Act. So, if you follow him, be patient.

Sample tweet: @finkd Tell your congressmen you want them to be pro-internet. My Facebook post is here ... .

Don Rickles

OK, maybe it's just because this one feels like such a time warp. He was born in 1926 and broke into the comedy business in the 1950s. But, by all appearances, that's really "The Merchant of Venom" on Twitter (witness the photo he posted with his dog Chauncey who, he explains, writes all of his tweets). He tweets at a clip of about once a day and, as you might expect, they're just about all zingers.

And by the way, you may ask ... whom does Don Rickles follow on Twitter? Nobody, hockey puck!

Sample tweet: @donrickles Just finished "Hot In Cleveland" - I keep telling Betty White I'm happily married 46 years, but she keeps saying we can work something out!

Queen Rania

It's not every day you find real-live royalty on networking sites. But not all royals are Rania Al Abdullah, the queen of Jordan.

She's answered questions of followers online and told interviewers that sites like Twitter can be used to achieve real social change. But we're particularly fond of her Twitter bio: "A mum and a wife with a really cool day job.. ." Her more-than 1.8 million followers seem to agree.

Sample tweet: @QueenRania V. special day. My youngest turns 7 & His Majesty 50! One life full of potential, the other full of accomplishments. #HappyBirthday

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