Looks like Taylor Swift is busy celebrating friends' birthdays by dressing up for the occasion. Last week, she was pictured with Dianna Agron in pretty vintage dresses in honor of Shirley MacLaine's birthday. 

And this weekend, Swift was busy celebrating another birthday - this time with her best friend Dianna Agron's 26th birthday! Cat lover Swift, 22, dressed up as a tiger! Agron's birthday party was circus-themed and friends wore costumes - including Swift, who went as a tiger!

Swift tweeted this weekend: "The most magical night at @DiannaAgron's circus themed birthday party." She tweeted the picture to millions of followers, looking very catty indeed. 

Meanwhile, Swift has come under speculation for having breast surgery after she was pictured in a tight dress with her bust looking more ample than usual. As rumors swirled online, even experts stepped in to offer their opinion.

Plastic surgeon Dr. Anthony Youn told Hollywood Life: "The country star appears to be following in the footsteps of another female country singer, Dolly Parton, and enhanced her breasts."

The reports were denied by the singer and her representative, which has come as a relief to millions of fans who prefers her to be natural in every way. 

SEE PHOTOS OF TAYLOR SWIFT'S MOST GLAMOROUS DRESSES ON THE RED CARPET

Tags: Taylor Swift dianna agron