Sometimes, it’s hard to tell how old people are in Hollywood!

From sexy singers and silver screen sirens to underage reality show stars, RadarOnline.com is playing a fun “who is older than who” game with the 20 hottest stars under 25, and you will be shocked with some of the results!

From the red carpet of the hippest events in the world to the city streets, Hollywood’s hottest stars were dressed in the best, worst & wackiest fashions over the weekend – and RadarOnline.com has all the photos.

While most people enjoy getting gifts on their birthday, Kim Kardashian treated her guests to an evening of white-hot sexiness!  The reality show star rung in her 31st in Sin City by showing off her famously curvy figure in a skintight, white dress, adding silver Christian Louboutin heels and
tons of white ice.

PHOTOS: The Best, Worst & Wackiest Weekend Fashions Round-Up

M.I.A. resurfaced at the London Film Festival premiere of Madonna’s new movie W.E. The Paper Planes singer missed the mark a la mode, donning a metallic jumper with a rather unique wrap and high-top sneakers.

The Gleeks were out in force Saturday night for the premiere of Glee:The 3D Movie in L.A.

Crowds started gathering around the Regency Village Theatre hours before the stars arrived and the photographers started shooting.

PHOTOS: Glee: The 3D Movie Premiere

Lea Michele, Cory Monteith, Kevin McHale, Chris Colfer, Diana Agron, Ashley Fink, Mark Salling, Darren Criss, Amber Riley, Harry Shum Jr., Jayma Mays, Heather Morris and Chord Overstreet were all there from the series.

Recent guest star Kathy Griffin brightened up the red carpet, and so did True Grit star and Glee-fanatic Hailee Steinfeld.

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Glee: The 3D Movie opens August 12 for a limited run.

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From the MuchMusic Video Awards in Canada to biggest Sin City soirees, Hollywood’s hottest stars were dressed to rock and shock over the weekend in the best, worst & wackiest fashions and RadarOnline.com has all the photos in our weekly feature.

PHOTOS: The Best, Worst & Wackiest Fashions Of The Weekend

Selena Gomez brought her steamy style north of the border for the Canadian awards show, rocking a super chic and sexy Burberry Prorsum mini on the red carpet. The Disney diva paired the tiny little thang with bright purple Giuseppe Zanotti peep-toes, dominating the red carpet. Also at the show, Avril Lavigne wore another Sk*er girl outfit (blah!) while Lady Gaga upped the wacky factor wearing one Versace outfit after another.

The glam factor was at the max at the 83rd Academy Awards on Sunday, as Hollywood’s hottest stars hit the red carpet in the swankiest designer gowns in the world.  Though you may not be able to afford the crazy couture and hot hooves that Anne, Halle, Sandra and Natalie rocked to the awesome awards show, RadarOnline.com has selected a few pocked-friendly options to help you get the look for less!

PHOTOS: Get The Oscar Look -- For Less!

Red successfully replaced black as this season’s go-to color, as Anne Hathaway, Sandra Bullock and Jennifer Lawrence all heated up the carpet in fiery fashions.

PHOTOS: The Best, Worst & Wackiest Fashions Of The Oscars

While Anne’s Valentino gown probably won’t fit into your monthly budget, we found a similar corseted and ruffled gown from the FLIRT by Maggie Sotero collection, which has the same look and feel as Academy Award host’s first gown of the evening, but will only set you back $288.  The gown is available online at Unique Vintage.

The red carpet was on fire Thursday night, as Hollywood’s hottest stars hit pre-Oscar events dressed to rock and shock - and RadarOnline.com has all the photos in our daily fashion feature.

PHOTOS: The Best & Worst Dressed Stars Of The Day

Elizabeth Banks showed off her sexiest side ever at the opening of the Tom Ford Flagship Store in Los Angeles. The Next Three Days star rocked a skin-sational Versace cutout mini dress from the Spring 2011 collection with green Miu Miu heels and a cool clutch, scoring herself the best look of the day.

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