Most corporate Twitter accounts are about as entertaining as a late-night  infomercial. They're trying to sell you something, they don't want to offend anyone, and any life or humor in their language has been wrung out by panicked public-relations or social-media employees who don't dare take any chances.

That's why it's such a treat to find a corporate Twitter account that gets it. A rare few accounts understand that an audience is much more likely to buy a product or use a service if the company involved displays a bit of personality.

It's a fine line to walk, because veering too far the other way can be a disaster. There's an entire meme dubbed "How do you do, fellow kids?" that points out just how embarrassing it can be when a company tries to fake hipness. (Hint: It's like how Bart Simpson feels when Homer wears his baseball cap backwards. D'oh!)

Here are three corporate Twitter accounts that deliver witty and entertaining posts while staying true to their brands -- plus a few tips you can steal from them to do the same.

1.     Charmin

Managing social media for a bathroom tissue account is as tricky as re-rolling the paper after your cat has gotten to it. The product itself can be awkward to discuss, and a too-casual attitude might flush away especially modest followers. But  Charmin manages to keep on rolling with a blend of pop-culture wit, an awareness of its social space, and yes, a good sense of bathroom humor.

Tip: Don't be in denial about your product -- surprise followers with your honesty.

Sample great tweet:

2.     Innocent drinks

Innocent is a London-based juice and smoothie company owned by Coca-Cola. But just because it has a gigantic parent company doesn't mean its tweets have gone flat. Innocent's social-media account stays fizzy and bubbly with tips about healthy eating that don't sound preachy, giveaway announcements, and gentle fun poked at news events, from the royal wedding to suggested signs for the London Marathon.

Tip: Tweeting about news events without sounding clueless or obtuse can be done, if you select the events carefully and maintain your own social voice.

Sample great tweet:

3.     Wendy's restaurants

No question, Wendy's is a big restaurant chain, but the company successfully plays up an underdog role on its always-witty Twitter account. Wendy's engages with customers, jokes about sporting events, and maintains an ever-fresh rivalry with a certain clown-run franchise over fresh vs. frozen beef patties. What could easily seem petty comes off as good-natured grilling of the burger king (not that Burger King).

Tip: Poking fun at the competition can work, if it's done smartly and without a sense of real malice.

Sample great tweet: