They find out after an accidental wish

The first two hours were flying by, even though Alex wasn't capable of focusing on anything that happened during those lessons. In his mind that scene with Cathy sucking his dick was running on infinite loop, and only incredible discipline kept his dick down in public. His very absent mind was easy to spot for Brian when they met in their usual spot during the break.
"Do we need to address the situation from this morning?" he wondered. The way that Alex looked back at him with his head still far up in the clouds answered the question sufficiently.
"I still might wake up from this." he started.
"If you dream of a full hour of geography with Mrs. Dankworth, then you have serious issues, dude." Brian countered.
"Maybe she just felt like it." Alex tried again.
"If she just felt like it, she could have gone to anyone, which makes this very unlikely." he noticed how Alex took this as an insult, and quickly added. "I mean she clearly didn't know about your dick beforehand, otherwise you would have been her first choice, obviously." Alex rolled his eyes with a grin.
"Magic?" he run out of options. Both suddenly looked at the ring he was wearing since today.
"Yeah, maybe it's a magic ring that gives you mind-control powers." Brian said with a chuckle.
"If that was true, she'd be here for a second time." Alex joined into the giggling. They both suddenly went quiet to see if that was actually the case, but obviously they still were mostly alone.
"Well then I conclude that it was your oversized member." Brian said as usual at this point "It's basic biology." It was no secret that Brian was into big dicks when it came to men. When it came to women though, he rather shared Alex' ideas of big boobs and asses.
"Maybe I subconsciously used the magic of this dragon ring to make her do that." Alex was playing yet another fantasy in his mind with Cathy playing the main, female role.
"In that case, could you use that magic ring to make my dick as big as yours please?" Brian kept babbling "It would certainly help me out on my advances." It was one of these annoying moments where he just couldn't stop talking about it, but it was understandable as he was probably as horny about the whole thing as Alex was, just from a different perspective.
"Dude... I wish your dick was twice as big." he said with a dramatic pause to make sure he had his attention "Just so you finally shut up talking about mine."

Brian stared at him with a strange look. Alex instinctively knew something was off, but he had no idea what it was.
"What did you just say?" Brian said like he had just seen a ghost.
"I told you to stop babbling about my dick." Alex repeated himself, unsure what he did wrong.
"No, I mean the wish part." Brian's gaze worried Alex enough to know something was wrong.
"I said: I wish your dick was twice as big." he repeated himself. Suddenly Brian's expression turned into pure shock, and his gaze went down to his pants. Unsure what was going on Alex looked down as well, and just in time to watch something... crawl down his leg?
"What the hell??" Alex exclaimed.
"Dude... when you said that wish thing the first time, I was sure my dick suddenly started growing in my pants." Brian explained "And when you said it again... well." He gestured at his absurdly large bulge that seemingly appeared out of nowhere.
"That is... impossible!" Alex reminded him, but it became more and more clear that this outline was not just something inside Brian's pocket.
"To the bathroom, I need to check this." Brian panted and marched onward as casually as one could with a gigantic dick. Alex had not much interest to see Brian's cock in general, but this time it was for science, so he followed.

"This thing is fucking huge!" Brian exclaimed, and held in his hand a schlong almost 8 inches long, yet still soft. Alex wasn't too fond of staring at someone else's dick, but he had to agree. Also he knew that Brian was just 5 inches down there, hard. "Sorry dude, but I need to know." Brian said and begun to pump his member. It was like a horrible car accident: Alex didn't want to watch, but he couldn't get his eyes off it. In grand disbelieve he watched Brian's dick expanding and expanding, till a massive pole of 20 inches of meat stood between them.
"That confirms it." Brian eventually commented the impossibly huge dick in the room. "The first wish doubled me to 10 inches, the second to 20." he concluded.
"But... how?!" Alex took his eyes off that cock and stared at Brian. Then their combined gazes went down to the ring.
"Quick: wish for me to be a total hunk with big muscles!" Brian demanded.
"I wish you'd be a hot girl with huge boobs!" Alex returned annoyed.
"Hey!" Brian protested, but immediately felt his whole body shifting in place "What the fuck?!" Alex couldn't take his eyes of his best friend changing shape like they were in a movie. That dick rapidly retreated into his groin again, while two mounds expanded on his chest at equal pace. Seconds later Brian still stood there, except he was now clearly female - and very hot - and also sported tits in porn-star size category.

"Why??" she complained, then noticed her changed voice. "Fuck, I even sound like a girl."
"Well I guess we can conclude that magic actually is a thing now." Alex stared at those gigantic knockers.
"Dude, my eyes are up here!" Brian reminded him, getting slightly angry.
"I know, but your boobs are down there." Alex defended his staring "Please look at them and tell me they are not worth staring at." Brian looked down, then reached for his new tits and squeezed them.
"I mean... you got a point." she panted from the unexpected spike of arousal. Suddenly Brian felt Alex hands on those tits, gently fondling them.
"So soft... like they are really real." Alex said absently. Since Brian was bi, she didn't care much about being turned into a girl. Also she trusted that man with her life and had no doubts that he would turn her back eventually. So for the moment she decided to just enjoy this fantasy becoming reality. She had been dreaming about Alex touching her like this often enough, and he would soon enough realize what he was doing, so she just stayed silent for the moment. At least until she couldn't keep the moans down anymore. This in turn ripped Alex out of his daze and reminded him who's tits he was at this very moment playing with.

"Uh... sorry... got distracted?" he grimaced. He knew Brian wouldn't mind too much, but he felt kinda odd to touch him... her like that.
"I let it slip." Brian still felt the arousal bouncing around in his mind. "If you could kindly wish me back now." Suddenly he panicked: "Oh god... I hope you even can undo wishes with that thing."
"I uh... I wish you were back in your old, male body?" Alex tried his best. Instantly his best friend started to change shape again, and just seconds later there was good, old Brian again, with an erection throbbing downstairs.
"Phew." he commented the transformation, and when he noticed Alex noticing his boner, he excused it with a grin: "Hey, what you did there with your hands did feel really good! You're a natural, you know..."
"Sorry for that." Alex repeated himself. "Had a strange day."
"Speaking about..." Brian decided to use Alex mental state for a quick, selfish request. "I think you didn't return my dick back to it's real size."
Alex stared at him confused for a moment, then rolled his eyes. "I am pretty sure I did."
"I am pretty sure it was bigger just a moment ago." Brian negotiated.
Alex sighted. "Ok, what size would you like it to be?"
"A nice... 14 inches?" he requested.
"Are you fucking serious?!" Alex knew about the problems guys had with a big dick, and his best friend was just requesting twice his size.
"Hey, you turned me into a girl, so I should get a wish, too!" Brian tried to look offended.
"Fine." Alex gave up "I wish your dick was 14 inches long." He would have to listen to this for hours otherwise anyways.
"Oh fuck..." Brian suddenly groaned and begun to rapidly masturbate his shaft while it expanded in his hands. When his cock reached it's final size just a few seconds later, and he could barely even wrap his hand around it anymore, he involuntarily came, and shot his load right against the wall of the bathroom stall.

"Dude!" Alex exclaimed. He didn't really want to watch his best friend cum.
"Sorry..." Brian was breathing heavily and with a very satisfied smile "That is my fantasy." They both stared at each other for a moment, then back at that impossible cock he sported now. Reaching all the way up from his groin to his chest this was an unnatural sight. It looked like someone had photoshopped a gigantic dick on Brian, yet it stood there throbbing and just very slowly going down.
"You know that's too big, right?" Alex reminded him.
"I fucking don't care!" Brian laughed "You know I read all those stories where guys get gigantic dicks all the time, and now it fucking happened to me!" There was clear bliss in the tears that run down from his eyes.
"I wasn't aware that you were so much into big dicks." Alex noticed surprised.
"Same as you are into big tits." he returned, knowing exactly what sizes Alex loved to stare at when he was alone. Alex didn't share his enthusiasm, but seeing his best friend that happy was reason enough to let him enjoy his fantasy for now.
"We should maybe figure out what else this thing can do." Brian eventually returned their attention back to the magic, wish-granting ring on Alex' finger.