I was scrolling through the list of badges, and got to the durtle section. The explanation of how to get these was really vague, but I saw a few users who for example had the words “Tomato Durtle” behind their name". Here is an image:
They just turned up one day and apparently are made from the charred shells of wanikani turtles. Bestowed from on high, some durtles are merit based and may be given out in response to behaviour that makes the forums a more welcoming, helpful space; while some are event based or perhaps even awarded at random.
I think everyone who got the tomato durtle actually grew tomatoes in real life last summer.