They're both gorgeous blondes with waves of glorious musical talent. They're also two of the most famous female stars ever to be spun from the ranks of 'American Idol.'

But sometimes their adoring public can't seem to remember which is which ... Is it Kellie Pickler? Or is it Carrie Underwood?

Bubbling with laughter, Kellie tells OK magazine that a lot of fans will call her "Kellie Underwood " and likewise, a lot of fans will call Carrie "Carrie Pickler!" But Kellie points out that she and Carrie are "totally different -- night and day."

Why? It's simple. Kellie says she's "crazy," while Carrie is "a lady."

Crazy might be a stretch, Kellie. But we'll give you adventuresome and definitely creative. Take, for instance, Kellie's own personal touch to her tour bus.

"I just designed my first tour bus, and I have a Sonic ice maker on my bus," she reveals. She also reveals that she straight-up stole that refreshing idea from Martina McBride.

"I love Sonic ice! Actually, Martina McBride -- she's a good friend of mine -- and she and her husband, John McBride, have a Sonic ice maker on their bus. That's where I got the idea! If they got one, then I'm gettin' one!"

Kellie says she and John are always laughing over their mutual love for the famous burger joint.

"John and I joke back and forth, because he loves Sonic," says Kellie. "I was like, 'Well, I used to work there

for three years, and I roller-skated burgers out!' And John goes, 'Well, that makes me want to tip you right now!'"

She may share her love of all things Sonic, but don't expect her to share that ice maker with too many people.

"I've been on my own bus for a while now, and I don't think I could ever share a bus anymore," Kellie told The Boot earlier this year. "That is my diva thing. I don't like to share a bus -- especially when you're traveling with a bunch of guys.

"You want to be able to get up in the middle of the night in whatever you're wearing -- or not wearing -- and go to the bathroom, or fix a glass of orange juice. I can't do that with a bus full of guys!"