urx unit loader 'Hills' honey Stephanie Pratt thinks Sandra Bullock was in 'Pretty Woman?' Oh, snap!

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Turns out Spencer Pratt's sister Stephanie Pratt is not as dumb as she looks.

She's way dumber!

At this weekend's press junket for "The Proposal," the highly entertaining new romantic comedy starring Sandra Bullock and Ryan Reynolds, the MTV guest reporter tried unsuccessfully to butter up Bullock by telling her that she was Pratt's grandfather's favorite actress.

Her grandfather?  Ouch.

To make it worse, Pratt continued, "Oh, he's dead now, but the two films of yours he used to watch over and over were 'Miss Congeniality' and 'Pretty Woman.'"

Bullock just smiled sweetly and said, "Well, if I were actually in 'Pretty Woman' I'd be very flattered."

Oh, snap!

Later, walking down the hall, a still chuckling Bullock got out her cellphone and started texting, telling a friend, "I have got to tell Ryan about this….."

Don't worry, he can read about it here.

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Photos: Sandra Bullock on the set of "The Proposal," and Stephanie Pratt doing what she does best at a party.
Credit: WireImage