Halloween costumes for adults always seem to necessitate the sex factor, especially for young women, but many of these costume ideas take the concept of cute and sexy and add some distinctly unattractive elements, giving us sexy costumes that really, really aren't.

Some of the best adult Halloween costumes leave something to the imagination, and cross the line between sexy and scary without creeping people out or (for women especially) going practically naked. Some of the worst sexy Halloween costumes, on the other hand, involve putting Hermione Granger in a miniskirt and spike heels and dressing sorority sisters like the Ninja Turtles.

For Oct. 31, 2011, try to avoid the ten Halloween costume ideas we've found online, ranging from Sesame Street characters and lingerie-clad Nurses to women in skirts and tops made to look like Spongebob Squarepants. Unfortunately, almost all of these Halloween costumes are made for women; we've added a couple, however, for those men who have really bad ideas around Halloween.

Here, see ten of the worst sexy costume ideas for women and men for Oct. 31, 2011. With Halloween just around the corner, make sure you aren't caught dead in any of these monstrosities!