James sighed. He normally wouldn't think of eating anything in this weird place, and was even having some doubts about the water he brought with everything else changing, but it obviously wasn't poisonous if Alan had been eating it this whole time, he'd left the snacks he'd brought back in the car, and it did honestly smell damn good. So in a gesture of good will, he took it and popped it in his mouth.
Moments after swallowing the mushroom, which did taste as good as it smelled, two considerations he'd overlooked suddenly struck him. This was a mushroom, and this was Alan. Sure enough, it wasn't long before the leaves started pulsating, tree branches started curling and flexing like fingers, and the glare of the sun shimmering on the water lifted off and flew away. Trails moved with his hands as he reached up to give Alan an angry shove for slipping him drugs at a time like this, but as his palms impacted his chest, they sunk in like he was made of pudding, and the two went crashing to the ground together.
Alan laughed in a strange way, sounding like he was simultaneously underwater, a record played at half speed, and like he'd huffed helium on every other chortle. As they hit the ground, which gave below them like a bounce house, Alan's arms transformed into snakes, constricting James and making it hard to breath. Fortunately, his body softened and pushed out from Alan's coils like a tube of toothpaste being squeezed into the water. James slithered along like a tadpole, eventually reaching the second surface at the lake's bottom and bursting into an upside down world, where he flew between giant coat racks and candy canes for what felt like hours, before eventually spotting an enormous donut laying on a cloud. After unhinging his jaw to swallow the donut whole, he curled up in the cloud for a nap.
James didn't come to until the middle of the night, and took several moments past there to realize that he'd come down from the halucinagens in that mushroom and returned to reality. Mostly because reality still didn't seem to be holding up its part of the bargain. He was lying on the side of a hill, with something large, heavy and warm on top of him, and something long and hard jabbing him in the thigh. In a mild panic, he shrugged off the weight and jumped to his feet, having a look around.
The first thing that struck James was the sky. Alan was right in comparing it to an album cover. A huge shimmering pink curtain hung in the air, with an absurdly oversized dull orange moon looming over the horizon, and another, more reasonably sized one in emerald green, hanging in the sky off to James' right. They cast enough light to see a bit, but the glint of the light reflecting off the lake was nowhere to be seen. Nor the forest that had surrounded it, or anything else at all familiar. They must have wandered away from the area while hallucinating. "They" thought James since that was almost certainly Alan he'd shoved away as he stood, most likely waking up as well, but all things considered, he really didn't want to turn around and confirm that, or look him in the face. In fact, he strolled down the hill a ways to try and collect himself a bit before confronting him again, feeling the strange alien grass between his toes, and a gentle breeze on his bare skin... all of his bare skin.
A quick pat down proved that yes, at some point while wandering around in a drug-fueled stupor, James had stripped off and tossed away the rest of his clothes. Moving his hands about his body also confirmed that he had indeed transformed into a woman. One with what at least from this angle felt like a plenty ample chest, rock hard abs, a nice round ass, and... yeah. A smooth, hairless mound with a slit he quickly pulled his hand away from. His face was smoother too. Nothing about it felt right. Dainty chin, little upturned nose. No wonder Alan hadn't recognized him.
James took another glance around for his clothes, or some recognizable landmark, but couldn't make out anything at all familiar in the dark. There was really only one sensible thing to do.