What to write back to this text?!?! FAST?

Okay so me and some guy are talking, we've gone clubbing a few times together and we havent even kissed yet. i want to show him im not easy like all the other girls he's dated. we were texting and i told him i was about to go shower and he said "oh sexy, can i join you :) ha ha" i dont wanna be rude causei know hes kidding but i wanna say something slick. something that will leave him thinking...any suggestions?