Ryan was at his local gym, he had begged his parents to get him a membership and take him, and eventually they relented on his 14th birthday. Ryan's wish was less of a conscious wish and more of a stated desire stemming from his feelings of hopelessness, "I wish I could just steal all that guy's muscles." Ryan started out small, and despite his efforts seemed to remain that way, so he felt cursed. In reality, he was in a growth spurt and all his muscle gains over the last 3 months kept him looking proportional.
The strange looking 'lucky coin' he found in the parking lot and slipped into his athletic shorts pocket that morning radiated with magical energy and changed reality building some kind of one way connection between Ryan and Noah, the random man Ryan targeted.
The first moments where Ryan grew to finally be muscular were amazing, 30 lbs of muscle does a lot! Ryan realized his idle wish was being realized and his curse was being lifted. He noticed Noah shrinking in all directions but height and decided to get out of the gym before someone realizes he somehow took the guy's gains.
What Ryan didn't realize, was that the guy was roughly 130 lbs of muscle. As Ryan was reaching the door, cries for help were heard and he slipped away unhindered and 50lbs heavier than normal. Over the next few minutes Ryan relaxed on the grass outside the building and just took in the feeling of his body growing, unaware of the chaos that was ensuing inside. As Ryan was nearing 200 lbs the man had lost around 2/3rds of his muscle mass and no longer had enough strength to support himself.
Ryan expanded to 240 lbs of muscle as Noah lost the strength needed to pump blood, breath, or move his food contents through his digestive system. Ryan now weighed more than most adult men, but had the small frame of a 14 year old who was 4-6 years from his full adult stature... bulky barely begins to describe him.
His wish was for the muscle which he now had. Unfortunately, his tendons and bone didn't strengthen as his muscles grew so he is one wrong move away from a severe injury. Ryan noticed he had stopped growing and decided to walk around town as he had accomplished all he wanted to at the gym already. Ryan was crossing parking lots as the ambulance pulled into the gym and didn't notice as they left several minutes later without its sirens.
Ryan checked himself out in a thrift store bathroom realizing he didn't quite look the way he wanted. Also, the people in his life will question him on how he changed so much. He has some things to figure out and an hour or so before one of his parents come to pick him up. If only he knew how his wish was granted in the first place he could wish for more things to fix himself up better.