The artist that made most of the art for Undertale and Deltarune uses krita for her artworks, her style is really cute, if you use krita you can draw like her if without downloading anything, as this brush is in krita by default.

You can find her on Twitter, Blue Sky.
@Tuyoki
@Tuyoki.bsky.social

Also as "Temmie Chang" in youtube, linked below, she has made some really cool animations

She also has some games of her own and a comic if you'd like to play and read, unfortunately steam doesn't like me writing links so you can find them by searching in google: "Escaped Chasm" and "Dweller's Empty Path"

Some of her art:

The brush is called "Block Fuzzy" under the krita 3 resources

You may need to enable this resource, you can do it by pressing this button and clicking the krita 3 resource.

She mentions using this brush in one of her streams:
https://youtu.be/7bEDKPKWDBU?t=1196

In that stream you can also learn about some of her sketching process and see some cute artwork.

With this guide I hope artists who know about UTDR but don't really know about temmie outside the game learn about her other work, as I find it her art really cool and I don't see her other work talked as much in the UTDR community

That's all, hope you have a nice day and keep drawing!