Jeff was experimenting and not really thinking about safety precautions or how an interdimensional gateway in his bedroom might possibly not be a the best thing.
Jeff had wanted to share the experience with his girlfriend, gone to school excited, tried to describe what happened, and received a flurry of questions interrogating his motives starting with why he would want to "do drugs," going through how the bartender is actually his victim, and ending on "even if everything you said was true, underage drinking is a major contributing factor to teen pregnancy," which completely made him rethink inviting her along or even continuing the relationship.
Arriving back in his room however he was greeted by his orange tabby, Oscar, perched on his computer desk, which was new... Upon offloading his backpack on his bed, Oscar yowled at him, then bolted into his closet. Jeff thought it was an odd action for a moment but then realized it meant the family cat was about to be lost in an alternate dimension!
Jeff raced through the door, going up to the barkeep, "Have you seen an orange tabby cat?" Jeff's voice, clothes, and body had already shifted. Now that he had a role in this universe, the transition was nearly instantaneous.
"One was here several hours ago, but disappeared, I haven't seen him since."
"Jeff," came an unfamiliar voice.
Jeff whirled around, alarmed to be known. Before him, a middle aged man stood gracefully, overdressed for the occasion.
"I brought you here to help me investigate this strange place. I half expected you to be a cat by now, but I suspect you are more helpful as a... man... yes. That's the word. I became human, you became man." Oscar clutched his head clearly struggling with going from animal intelligence to human intelligence.
"Oscar? You're a person now!" Jeff exclaimed.
"I just said that!" Oscar snapped. "I'm trying to understand what this place is and where it came from, but with this body come... so many thoughts. I need help Jeff, I explored this place all day but can't smell anything but the strongest of smells. I can't even detect the odor that brought me here in the first place."
Jeff paled, he never meant to give the family pet human levels of intelligence, even in an alternate dimension. "Oscar, this place isn't for you, if you go back to my room, you can be a cat again and forget all about this."
"No, I need to understand this space that wasn't here before! When I become a cat again I can't think like I can when I'm here, I remember being here but it is strange and confusing."
"I made this space, for me to have fun, get away from family, try new things, and look like this. You don't need to worry about this space, I control it."
Oscar looked at Jeff with a judging glare that only a cat could muster, "Everything from my cat life and human man life tells me that isn't how things work. "
Jeff squirmed under the scrutiny, "Normally no, but my computer... the box I sit at and stare at for hours in my room, it let me make this space."
Oscar pondered, and became lost in thoughts. All the curiosities he had as a cat, as a man he could answer with basic human knowledge, every strangeness about humans, answered by the social convention he inherently knew.
"r... hey Oscar.... Hello, are you ready to go back home?"
"You never ate any of the mice, frogs, or birds I caught for you..." Oscar looked at Jeff with devastation.
"No, no we didn't. But we knew it meant that you didn't want us to die and we appreciated the sentiment."
"See if I leave you anything else to eat..." Oscar replied indignantly.
"Oh, we know you care for us, and that's enough, it would actually be better if you didn't bring us dead animals. Or live ones! Just to be clear."
Oscar wanted to be upset but of the time he had been in this space, processing things with memories as though he was a human for the last 38-44 years, all he could say was, "Right, that makes sense I guess." Concepts of a grocery store, capitalism, work, and the world economy fighting for his focus.
"Are you ready to come home yet?"