I feel like if the WK staff member who implemented this feature is reading this thread (hi!), they must be laughing so much about all the obscure pop culture references we’re coming up with here.
(My hypothesis is that these are not supposed to be references to anything, but they simply sorted the filenames alphabetically and assigned them to 42, 84, 126, …)
I swear berry red shows as light red/kind of pink on my widget. Maybe it’s a shiny berry durtle :3 
https://assets.wanikani.com/assets/widgets/study-streak/berry-durtle-d41dc8f5.svg
that’s because of the theme you’re using
my fred has a pink hat when the default is blue
oOoooOoooo another hypothesis to test ワクワク 
Yeah, most likely so.
This is the one, thank you!!
Hi! My contribution is day 462
His name is Goopy Durtle
https://assets.wanikani.com/assets/widgets/study-streak/goopy-durtle-1236cde6.svg
Good work!
Wow…it really looks like the durtles are just sorted alphabetically. There’s no deeper meaning? 
Maybe the deeper meaning is all the friends we made along the way 
The real durtle was inside you all along.
And it’s gonna come bursting out of your chest when you least expect it.
Day 840 here. “Advanced Durtle”, huh.
https://assets.wanikani.com/assets/widgets/study-streak/advanced-durtle-72d27605.svg
wow, that one’s… interesting 
Wow that’s quite a shocker to see in the morning.
It’s theoretically the last durtle so this debunks the alphabetical sorting theory by @willem3141. 
I wouldn’t say debunks just yet tbh. If every other durtle is alphabetical, I’d just assume this is a special exception to the rule, given it’s the last one?
Interesting! I think the advanced turtle “counts as” the turtle that you’d get on day 0. Of course, WK never shows a streak of 0 days, so the first time you see it is on day 840.
Or for any programmers among us, my hypothesis is that the code works like this:
if (streakLength % 42 == 0) {
let specialDurtles = ['advanced', 'alien', 'berry', ...] // alphabetically sorted list of 20 durtles
durtleToShow = specialDurtles[(streakLength / 42) % 20]
} else {
durtleToShow = 'normal';
}
Ahhhhhh that’s clever, makes a lot of sense 