This is some more classic Carbine humor. Randomly killing a rat in Fort Glory gives you a challenge called “Seriously?” which asks you to – you guessed it! – kill rats! This is a hilarious take on the classic “kill ten rats” quest in MMOs, and it pokes fun at the genre by giving it that title. It actually gave decent rewards at least! And it is optional!
Side note: the addon above the chat window on the left is called Radar, made by Packetdancer herself. It is one of my favorite addons in the game, second only to Deadlock (which locks your view to your mouse). Radar allows you to track resources and lore objects, and it even allows you to ping them and point an arrow to them. Pretty awesome, great for finding out-of-the-way lore items.