PORTLAND — The children who once dreamed of capturing real-life Pokemon starting in the 1990s are now the nostalgic millennials helping fuel the worldwide success of “Pokemon Go.”

Take Bailey Richardson. Now 26, her grandest dream was once to set out in the world and capture and train the big-eyed, shrieking creatures known as Pokemon, originally numbering 151 in all.

On a recent night, she was outside playing “Pokemon Go” when someone shouted that they had found Aerodactyl, a rare, pterodactyl inspired monster. It was raining, but she joined everyone around her, running down the street in pursuit of the ancient creature.

“I think the nostalgia element makes it so easy to talk to strangers,” Richardson said while exploring downtown Portland this week. “We share these roots.”

In between glances at her smartphone to check for nearby Pokemon, Richardson reminisced about choreographing endless dance routines to the “Pokemon: The First Movie” theme soundtrack with her cousins and brother.

“As much as I love this, if it hadn’t been Pokemon, I wouldn’t be playing,” she said.

In the fall of 1998, Pokemon mania hit U.S. shores as Nintendo released its popular “Pokemon” Game Boy games and a companion television show hit the airwaves. Soon, the cartoon creatures who shrieked their own names were everywhere: trading cards, comic books, stickers, movies, a catchy rap song.

About 90 percent of adults who have downloaded the new “Pokemon Go” smartphone game, which lets you find cartoon monsters in the real world, are between 18 and 34 years old, according to mobile advertising company StartApp – many of them old enough to have fallen in love with Pokemon the first time around.