Queenigma is a bounty plant in Plants vs. Zombies: Battle for Neighborville. She resembles a Rose wearing the Fairy Queen costume. She can be hunted in the Weirding Woods near the starting point. Defeating her unlocks the Diss from a Rose medal.
Her name is a portmanteau of the words, "queen" and "enigma."
Queenigma is invincible when the spawned mushrooms are still present, as hinted by the "halt truffle kerfuffle" objective. Use the Super Brainz to take them down quickly. The Night Caps can be killed in one hit by using a fully charged fist, preventing her from turning invisible. Once they are taken care of, you have 20 seconds to defeat her before she turns invincible again, spawning even more mushrooms, so just attack her quickly with the fists until she is defeated.
Coin, marshmallow, and XP farming
Please note that this method is no longer efficient. The XP and coin yield of bounty hunts has been reduced by 10x and marshmallows from bounty hunt completion are no longer awarded due to an unlisted nerf in the November 2019 Patch.
This bounty hunt can be exploited to quickly farm coins, marshmallows, and XP, especially in single player, as it is relatively quick to perform. However, this farming method is less efficient than the Bitey Brothers bounty hunt as the XP yield is lower. This is further pronounced after the November 2019 patch, where the rewards for subsequently completing bounty hunts have been reduced significantly.
Simply use the Super Brainz with Fearless and Leveling Up upgrades, and defeat her multiple times until you get the desired amount of them. Beating this bounty hunt gives you at least 500 coins, 2-5 marshmallows (from enemy loot drop), and 160 XP (179 XP with Leveling Up), and it takes around 30-45 seconds to defeat her with only one player.