Source:https://www.indiewire.com/2013/09/behind-the-scenes-wander-over-yonder-122658/>Jerry Beck: Is this Flash animation? Someone said that it’s being
done on computer, but obviously you’re drawing it.>CM: It’s done in Toon Boom Harmony, a program almost like a
mix between Flash and after-effects. With Flash you draw a character, clean it
up, illustrate it and put it in the computer
where you can slide it around
like a toony virtual puppet What
they’ve done up at Mercury Filmworks is basically liquefy our toony drawing and
sculpt it into any pose. So, if we send a special hand-drawn pose, and tell
them this is what we want the character to look like, they will take the
virtual 2D puppet and mold it to that drawing, or even redraw parts if they
need to . It’s a weird mix between 2D and 3D . All the original pieces are
based on drawings. With all these different planets and characters, it’s even
more complicated because you’ve got to have new puppets for every single one. I
really admire the “ink lines”, even though there’s no ink involved. It’s
smooth, really great.
So not /literally/ Adobe Flash, but a similar process. It's not the same process as OK K.O. or Amphibia.