Upset Tony said "Turn me back!"
A bit unsure you asked "Um... You boys have... Something between their legs right?"
Tony thinking a little weirdly asked "Yes, it's a very important part of being a boy... Are you trying to tell me that you can't really make me a boy again since you don't know about a penis?"
You said "Yes. I know my body well enough and... when I spread out my magic a little. Well it was easiest for me to picture a girl. I mean I also can picture hawks, deer, and squirrels if you'd prefer." Tony went to to her computer and motioned for you to join her.
Tony turned it on and said "Well if you can't turn me back without knowing about what's going on on our crotches. I'm just going to have to show you one..." then she turned to an incognito browser and looked up some porn. Tony managed to find a male human pov of sex and then played the video. It was stimulating to say the least. Your face was flushed red for most of it and you felt kind of odd and tingly during parts and your crotch felt a bit tight after the video ended. Tony asked "Well do you think you could make something like that?"
You said "...maybe..." then kinda felt like a tail being crushed in some trousers in your crotch area. To look you saw that you had subconsciously activated your magic to create a small penis with testicles. A bit red faced at embarrassment and sexual curiosity the small penis hardened and your magic combined with it making the boner longer and girthier.
Tony stared at it and said "That's a penis all right..." a little embarrassed as well
You asked "How do I get rid of it?"
Tony said "I don't know, don't you have your magic or something?!?" You put your hand on it and tried to push it in however it was closer to masturbation and unknowingly you had made it a lot more sensitive than a dick usually would be, and as such cummed rather quickly over Tony's female body dressed in his boy clothes. Calming down and unhardened you were able to get rid of the thing, replacing it with your normal vagina. Tony said "Just forget turning me back into a boy right now. Calm down, and let me borrow some of your girl clothes. You'll then turn me back to normal after we return from dinner... Just call me Tina when we're out, it'll invite less questions."
You nodded and went to some of your things and had a pair of clothes for your 16 year old human body and clothes for your underdeveloped elf body for girls around 8. One of which was a little too big and one of which was definitely too small. You asked Tina "Well... Do you want to become bigger or smaller."
Tina said "Just make me bigger." and as such you extended your tendrils of magic as Tina was undressing to prepare for the outfit and she gasped for a second as her body extended upwards as her hips widened and breasts grew a bit. Tina got into her clothes and said "Wow didn't know you could age someone."
You said "I wasn't quite sure I could either... I think this particular magic may wear off in a couple of hours."
Tina said while finishing up dressing "Well we're only going to be out for an hour and a half at most so we have enough time." The two then started to go out into the city and go eat, and Tina showed you around a shopping center real fast before returning home where...