Well, you are wearing your clothes, there is some ID in your wallet. What the heck; she would have been a complete idiot if you believed you were your own twin sister, or cousin, or some relative that you've never mentioned to her before.
You try your best to muffle you've voice. "I am here to see Emily." you say to Amy. "Emily, there is a visitor here to see you." Amy shouts into her apartment. "I'm in the shower comes a distant voice." (Odd, there is no water running.)
"So, how do you know Emily?" Amy inquires, trying to pass some time.
Oh, wow, Amy doesn't recognize you, that's strange, you didn't think you looked that different. Maybe you should deepen your voice more.
"Oh, I promised I'd take her out tonight.---I'm her boyfriend." you say after Amy looks at you silently.
Amy has a look on her face that doesn't know if you're being funny, or if Emily has become a lesbian. (Maybe she's just dating a cross dresser.)
"Oh." says Amy, and then stays silent.
Emily finally comes out of the bathroom, with a towel around her her torso, and hair.
"Who's this?" asks Emily as she walks towards her room.
"Your date." says Amy.
"Oh, I didn't realize that I was a lesbian." said Emily.
"Don't tease." you say. (Wait, you'd never say that!)
This stops Emily. She then looks at you, something about your voice is familiar. It is higher pitched than usual, but something is still there.
She then gets a good look at you. "The hair is longer, but you do look like him." she says.
"That's because I am him...I mean me." you instantly respond.
"Nonsense. Emily's boyfriend doesn't have these." Amy says as she lightly slaps your chest.
(OUCH! she hit you too hard.)
You let out a girlish 'yelp.'
"Fine, I'm leaving! But before I go, I think I should tell Amy where you're birthmark is." you say, frustrated that Amy hit you, and nursing a growing instinct to run to a corner and cry.
That got her attention. The Next ten minutes involve you trying to explain your current situation.