1994
Stan Pines knew trouble when he saw it, and the guy with gray hair who was on his second tour of the Mystery Shack had a great big 'T' tattooed on him. So Stan was a little surprised when he saw him waffling between buying an ice cream bar and a small plush jackalope in the gift shop as the rest of the last tour group was drifting out. Given that Stan knew, from his own experience, anyone wearing a coat like that wouldn't hesitate to shoplift the jackalope (shoplifting ice cream bars tended to get messy) his interest was piqued.
"No discounts. No refunds. We close in five minutes," Stan said to break the ice. The guy turned to look at Stan, and oh gods, he was just a kid.
"Yeah, kinda guessed that," came a response that was just bordering on a growl, in a register that suggested the kid was pitching his voice lower to sound older, "so whaddaya think, pointless sentimentality over the only person to treat me decently?" he held up the jackalope, then nodded at the freezer full of ice cream bars, "or dinner and still have some money to get gas to get to the next city? I try not to steal anything in a small town; they can get...weird," and finished with a bitterly mocking smile.
Stan Pines was not a nice man, he'd argue that he wasn't even really a good man, but giving the kid a good looking over made him feel ill. Stan knew this behavior. He knew what caused it. He knew he should just shove the stuffed animal and ice cream into the kid's hands and tell him to get out.
He invited the kid to stay for dinner.
The next day he contact an old acquaintance who was good at 'paperwork.'
A few weeks later Stanford Pines had the documents to prove the teen was none other than the long lost son of his brother Stanley, Dashiell Xenon Pines, and that as a good brother he was adopting the poor parentless kid.
Frankly out of all the dumb things Stan Pines did in his life, this was the one thing he never regretted.