*it's a normal day in the Titans tower, Starfire is walking through the house and passes by Robin as he drops something*
Robin: Ooops. *bends over to pick it up, and Starfire sees and her eyes widen, and she grabs her crotch*
Starfire: Uhhh...
Robin: You ok, Star?
Starfire: I am the fine, I just need to... *rushes back to her room*
Robin: Meh. *walks down the hall*
*a half hour later*
*Robin goes into Starfire's room*
Robin: You wanted to see me?
Starfire: Yes Robin. There is a secret I have been meaning to do the revealing to you.
Robin: Ok, what is it?
Starfire: I would rather do the showing, but I will need you to do the turning around.
Robin: Huh?
Starfire: Just turn around and do the pulling down of your pants.
Robin: Um, okay... *turns around, then pulls down his pants as Starfire removes her skirt and pulls downs her underwear, revealing a penis, which she then sticks into Robin's butthole and begins thrusting, confusing Robin, who gives both a confused and pleasured look on his face as Starfire continues thrusting*
*after a few minutes*
*Starfire pulls her penis out, and sprays cum on both of Robin's buttcheeks, then into his butthole*
*a minute later*
Robin: Starfire, when were you gonna tell me you were a futa?
Starfire: What is a futa?
Robin: It's where a girl has a penis.
Starfire: Well, male tamaraneans are the ones that do the giving birth.
*Robin gives a confused stare for a few seconds*
Robin: I guess that makes sense...
*Starfire giggles and kisses Robin on the lips*
Robin: Well uh, see ya around... *exits the room*