-Happy birthday to Aly Michalka!

The actress/singer turns the big 21 today! Aly is currently filming a pilot for the CW called “Hellcats,” co-starring Ashley Tisdale and Gail O’Grady. The show centers on Marti (Aly Michalka), a college girl from the wrong side of the tracks who, after losing her scholarship because of budget cutbacks and her mother’s (Gail O’Grady) chronic irresponsibility, joins the Hellcats, the college’s competitive cheerleading team.

Ashley, who dyed her hair brunette for the role, stars as Sierra, the peppy and fiercely intense captain of the Hellcats who, after an initial clash with Marti, her new roommate, realizes that she just might be the godsend the Hellcats need to win the championship.

Little sis AJ wished Aly a happy birthday via twitter: Happy Almost Birthday to my best friend Aly I love you sis…21!? What?! Wow…are you sure?! Hehe Xo AJ

Also celebrating a birthday today is Sean Faris. Happy birthday!