phot: Getty Images

Looks like President Obama new how to get the girls! Check the pictures of the Hottie he took to the prom HERE!

Here's something we see roughly every third day or so:  RIHANNA Tweeted a picture of her nearly-naked ass yesterday.  It's from the set of her new video, "Pour It Up".

She's wearing a pink thong underneath a pair of denim shorts that's so cut up it doesn't even cover the thong. 

A lot of people are wondering if Rihanna posted the pic to get back at CHRIS BROWN . . . who was spotted with his ex-girlfriend Karrueche Tran this week.

Perhaps she was also bothered by the photo Karrueche posted on Saturday . . . in which she's shoving her naked butt into Chris Brown's face.

Saturday was Karrueche's birthday . . . and the caption on the pic says, quote, "My birthday last year.  Who's face am I gonna put my ass in this year?"

Rihanna seems to have deleted her butt-shot, but luckily, the Internet is still hanging onto it. 

(Check out both of these classy pics HERE.)  (Daily Mail)

Where does your ding-dong and woo-hoo get hurty?
Here's the latest research:

    Clothing - 32.4% of all penis injuries and 8.7% of injuries overall. Two-thirds of these are There's Something About Mary-style zipper injuries. It's amazing that button flies never truly caught on. It seems shockingly barbaric that we still keep our genitalia within centimeters of a bunch of metal teeth just desperate to attack. And you've never heard of someone accidentally hurting themselves by buttoning his penis, right?

    Another interesting stat in the "clothing" category: 3% of all injuries to the genitals were from footwear. I'm not sure if that includes kicks to the groin or not, but otherwise, how do 44 people every year go to the emergency room with footwear-related genital injuries?

    Toilet, shower and bathtub - 5.18% of injuries overall. The bathroom is one of the most dangerous rooms in the house for the genitalia. The researchers found that the primary toilet injuries happened from "a toilet seat crushing a man's penis or scrotum." I have no idea how the mechanics of that work -- how do you ever have your penis/scrotum at an angle where they're crushable? -- but it's enough to send more than 200 men to the hospital every year. As for the bathtub and shower injuries, most are from hot water burns... but some are from people accidentally ramming into the faucet or handles.

    Razors, scissors, and hair clippers - 6.9% of injuries overall. Based on what I know from the adult films of the 1970s, I bet this is the fastest-growing category over the past three decades.

    Bathing products - 16.1% of all injuries to female genitalia and 4.8% of injuries overall. This mostly comes from irritation from the chemicals in soaps and shampoos. Although that can also happen from scrubbing too hard with a washcloth or loofah. Or accidentally overdosing on Nair.

    Furniture - 10.3% to testicles, 11.6% to female genitalia, and 9% overall. The majority of furniture injuries happen when someone either straddles a piece of furniture or tries to jump or step over a chair. Seriously, don't try to jump over a chair. About 500 people a year go to the hospital because they hurt their groins on the backs of chairs. That's 3.15% of genital injuries.

    Sporting balls to the groin - 5.34% of injuries overall. Footballs in the groin account for 1.2% of all genital injuries every year. Other less iconic balls like basketballs, soccer balls, baseballs and softballs account for the rest. And probably tetherballs too.

    Bicycles - 7.67% of injuries overall. Bicycles account for the most injuries of any specific item. (A lot of these injuries happen on men's bikes because of that top bar. Women's bikes still don't have that. Maybe you should switch to a woman's bike. Or an old-timey bike with one giant wheel and one tiny wheel. It's virtually impossible to crotch yourself on one of those.)

    Sex toys - 4.3% of injuries to penis and 8.6% to female genitalia. Of these injuries, 39% are from phallic devices and 35% are from penile rings. The researchers didn't go into detail on what toys cause the other quarter of these injuries, but you can bet people get stuck in inflatable dolls and chastity belts more than they'd like to admit.

    Flooring - 8.8% of all injuries to senior genitals. The only age group whose genitalia are under attack by the floor are people over 66.(Primarily through falling down and having the groin hit a hardwood or tile floor.) But only about one in 13 genital injuries happens to people in that age group, so, basically, don't worry about the battle between the floor and the groin. It's an obscure one.

    Climbing equipment - 4.9% of injuries overall.Climbing equipment means things like ladders, stools, and even stairs, Which is surprising, because with the way that rock and mountain climbing gear straps between your legs, you'd think it would outperform ladders and stairs.

    Sports vehicles - 3.39% of injuries overall."Vehicles" was an odd-ish choice by the authors, since this isn't just about ATVs, it also includes horses.

MIRANDA KERR accidentally flashed her breasts during a photo shoot.  And thank whatever gods you worship that the intrusive paparazzi were there.  (You'll find the photos HERE.)

KATIE HOLMES got into some wet T-shirt action on the set of her new movie.  (You'll find the pictures HERE.)