Aside from her newest hit song "Roar," Katy Perry revealed during an interview at the iHeart Radio Music Festival that she is "so OCD." The award winning singer may have been perceived by most of her fans and followers as all glamour all the time, but in between here and there, she always wants everything organized.

According to E!Online, it's something even more intense than just keeping her schedules tight and well planned. Ms Perry told radio host Elvis Duran that she even wants everything in "alphabetical order." The 'Prism' singer also added that she's a bit obsessive compulsive when it comes to germs.

As for the rest of her interview, she focused on recalling the days when she was still a struggling artist and how much she has been grateful for radio. "I feel like my relationship with radio is super important. I feel that's more than half the reason I have the success I have," the 'Hot 'N Cold' singer shared.

She also spoke about Elton John as someone she looked up to in the run of her career.

As for the other celebrities who suffer from the same OCD habits, here are some of the most popular ones you surely know:

Megan Fox

The hot star's OCD is related with "intense awareness of germs," according to Mandatory.com. She does not want to use any public rest room or even use any silverware in restaurants.

Cameron Diaz

The fear of germs goes the same for Cameron Diaz who has always been open to the public about her disorder. Her fear is related with doorknobs that she insists on opening them instead with the use of her elbows. She washes her hands at multiple times each day.

Justin Timberlake

This former 'N Sync singer is self-diagnosed for having OCD with a mix of ADD or Attention Deficit Disorder. One of his weird behaviours include having all the food items he needs in his refrigerator.

David Beckham

The recently retired player and husband of Victoria Beckham turns into agitation when he sees things like furniture in hotels not aligned well. He once admitted that living with such a disorder can be tiring since when he does not give in to it, it still makes him feel tired since he can't stop thinking about settling it.

Check out the slideshow for other well known celebrities who have OCD!