Dropped a Bridget On Him/Sandbox

Sexual attraction is a funny thing, and sometimes if a character physically appears to be the right gender to appeal to their sexual preference, then they'll become attracted to them, regardless of what that character's actual gender might be. Usually said character's true gender is being kept secret purposefully and they are a male Disguised in Drag or a female Disguised As Male, but whether the misunderstanding was intentional or not, due to Rule of Drama, they will find out and it will be awkward, hilarious and possibly traumatizing for all involved.

This can happen to either gender of any sexuality. A male might be shocked to find the girl he's been crushing on is a male all along. A female might be confused to realize that hot guy she's been daydreaming about was actually a woman. Her male Gay Best Friend, who was also daydreaming about the guy (who is really a girl) will probably feel similarly. Almost always there is shock upon The Reveal, possibly even some disgust, anger or disappointment on the part of the character who was feeling the attraction, but usually the two characters can reconcile by the end and become friends. Other times it might not bother them, or after a period of consideration, they'll decide If It's You It's Okay.

This is both a reveal trope as well as a character reaction trope, when what initially appears to be compatible gender attraction is later revealed to actually be incompatible gender attraction (Example: Straight boy likes a girl, girl turns out to be a boy). It is a sister trope to the related Sweet on Polly Oliver, which refers to when what initially appears to be inexplicable incompatible gender attraction is later revealed to actually be compatible gender attraction (Example: Straight boy likes a boy, boy turns out to be a girl).

Compare with Shapeshifting Squick, Dude Looks Like a Lady, Bifauxnen, Gender Blender Name and Samus Is a Girl. Often accompanied by Attractive Bent Gender. Contrast Jumping the Gender Barrier and She's a Man In Japan.