Paper Mario Roleplay

Paper Mario Roleplay was one of the most popular roleplaying games on Roblox, having a total of 5.1 million visits, nearly 50,000 favorites, over 12,000 likes and 1,552 dislikes. Unfortunately, the game was reported and deleted on August 14, 2018 from an unknown player, most likely an employee who works at Nintendo, meaning it was deleted for having copyrighted material in it.
 * Many similar versions of the game have continued development on the Roblox gaming platform, despite previous challenges faced with maintaining Paper Mario Roleplay.

The Flip Flop
We can't possibly imagine the flip flop sticker is worth the price, but those who somehow managed to accumulate enough Star Points to buy it will be rewarded with this badge when they use it.

The Flip Flop Badge is rewarded when the player collects at least 99,999 Star Points and uses the item, which transforms the player into a sandal morph.

MAR10 DAY!
You played on March 10th (Mar10); Mario Day!

The MAR10 DAY! Badge is rewarded when the player plays the game on March 10th, which is Mario Day.

Egghead
''You found 8 of Yoshi's lost eggs during the Yoshi's Egg Hunt event! You now have access to a special egg sticker!''

The Egghead Badge is rewarded when the player finds eight Yoshi's Eggs around the map, which also rewards the Yoshi's Egg item, meaning the badge and the item are only obtainable during the Yoshi's Egg Hunt event.

Links
Current half-official* continuation: RP Extravaganza

* The term half-official means the game isn't officially made by Dogon (although he had plans to do it) but picked up by ex-PMRP devs.