Lókomon
Lókomon, wild creatures that fill the world. Very few are small enough to fit in a pocket. They're generally fearful of humans, and very few have been domesticated.
For all of human history, people had dreamed of taming and even befriending these creatures. Professional Lókomon-whispers can have them do basic tricks.
Capture Device
Due to a great leap in technology, devices are now available which made the temporary "capture" of Lókomon simple. These devices, looking vaguely like polaroid cameras, use quantum mechanics (or something) to store Lókomon in device which look vaguely like polaroid pictures.
Capturing a Lókomon will not usually endear it toward you, (especially if you had to wear it down by sending your own Lókomon to wear it down) so before you can train a Lókomon, you'll need to spend time befriending it.
And due to laws requiring the humane treatment of Lókomon, these devices become inert and release its occupant. (Imagine what could happen to a Lókomon left forgotten in a child's dresser drawer for years...)
Ticket to Ride
In Railfan, you travel exclusively by railroad that criss-cross the region. No "world map" is available, because the world is generated as you travel. Large cities have lots of travelers and branching lines, towns have more residents with quests, and local train spots have easy access to the wilds where you can find more Lókomon.
You'll also spend as much time on the train as off the train. Interact with travelers, look out the window to spot local Lókomon, and learn about local events or suspicious activities in the area.