Wednesday, we celebrated the most hallowed of holidays, National PDA Day. Now, to show what happens when PDA goes wrong, we bring you the worst celebrity kissses.

So, how do these less than sexy smooches make our "worst of" list? Three important qualifications:
1. Unlikely pairings/ awkward participants
2. More slop than smooch
3. Overall "ick" factor

Kim Kardashian and Kris Humphries' doom-tinged kiss, Paula Abdul and Simon Cowell's cringe-worthy lip lock and Will Ferrell and John C. Reilly's manly makeout session all make the cut. These stars certainly know how to turn it on (while turning us off!) for the camera.

Check out the worst celebrity kisses below, learn from their mistakes and put your newfound knowledge to good use. After all, this is the one day a little PDA is totally acceptable.

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  • Janice Dickinson

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  • Sharon Stone

    (FameFlynet)

  • Meryl Streep And Sandra Bullock

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  • Gene Simmons And Shannon Tweed

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  • Vanessa Hudgens And Austin Butler

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  • Jason Segel And Russell Brand

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  • Steven Tyler And Carrie Underwood

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  • Michaele Salahi And Neal Schon

    (RumorFix)

  • Kris Humphries And Kim Kardashian

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  • Al Gore And Tipper Gore

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  • Prince Albert And Princess Charlene

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  • Liza Minnelli And David Gest

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  • Angelina Jolie And James Haven

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  • Jennifer Lopez And Ben Affleck

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  • Betty White And Jay Leno

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  • Spencer Pratt And Heidi Montag

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  • Sandra Bullock And Halle Berry

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  • Busy Philipps And Michelle Williams

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  • Kristin Chenoweth And Sean Hayes

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  • Will Ferrell And John C. Reilly

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  • Paula Abdul And Simon Cowell

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  • Eva Mendes

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  • Prince William And Kate Middleton

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  • Elton John And Nicole Kidman

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  • Sharon Stone And Kathy Griffin

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