Miley Cyrus was ''plain old nice'' when she guest starred on 'Saturday Night Live'.

The singer-and-actress delighted the cast and crew of the comedy sketch show when she appeared recently with her down-to-earth attitude and lack of diva antics.

A source said: ''Everyone expected Miley to show up with major attitude - but were stunned when she turned out to be a major sweetheart.

''She went out of her way to be kind to everyone - just plain old nice - posing for pictures backstage and signing autographs for the crew.''

Miley, 20, also impressed the show bosses with her strong work ethic.

The source added to the National Enquirer magazine: ''And even though she's the most famous person on the planet, she was totally down-to-earth throughout long days of meetings, rehearsals and performances with the 'Saturday Night Live' stars and never displayed an ounce of attitude.''