Mary's whole "I'm bisexual" prank was really a Secret Test of Character.
- She says it to see how he reacts (he's uneasy, but is ok with it), whereas if he said something like "Eww, that's disgusting", she would drop him on the spot.
http://tvtropes.org/pmwiki/pmwiki.php/WMG/TheresSomethingAboutMary
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