How to get rewards in Animal Crossing: New Horizons' Stamp Rally
Get gold plaques for nerding out at the museum.

Your reward for completing the Stamp Rally. (The plaques, not my empty room.)
If you've checked in to your island in Animal Crossing: New Horizons any day after the 18th, you've no doubt heard about the Stamp Rally . It's an event taking place in your island's Museum commemorating International Museum Day (duh), and lasts from May 18 to May 31. It's not as expansive as other events, like Bunny Day or the mushroom DIY recipes, but breezing through it will get you gold plaques, like the ones you see on the walls of Blathers' museum.
To complete the challenge, go into each of the three museum wings and find these yellow and red stations. There are nine in total.
How to Stamp Rally
If you go into the museum, Blathers will talk your ear off about the Stamp Rally. You know how much he likes to chat. It's simple. Throughout the museum's three wings -- fossil, bug and fish -- you'll find three yellow and red Stamp Rally stations. (That's nine in total.) Interact with them all to fill out your stamp card. These stations will randomly change location each day.
Once your card is fully stamped, talk to Blathers. He'll be stoked, and he'll give you a gold plaque for each stamp card you fill out -- you'll end up with gold fish, bug and fossil plaques. You'll be able to complete this in under 10 minutes, easy.
Blather's gets increasingly more stoked about your progress through the challenge.
Once completed, you can go back to fishing, digging, bug catching, terraforming or whatever it is you like to do on your island. The next big thing coming to Animal Crossing: New Horizons is Wedding Season. It'll last through the month of June, and will be all about photography.