PewDiePie mentioned I am a cat by Natsume Sōseki 2 times

On Felix's bookshelf.

First off we have 'I am a Cat' by Soseki Natsume. It's a Japanese writer who spent some time in England and then he came back and then he published this in a magazine only I think the first chapter he wasn't planning to make it into this beast that it is today but people liked it so much that he kept publishing it and uh yeah maybe that's how you were supposed to read it just like in parts here and there. [...] This book is a satire, it's a very old satire but that doesn't stop it from being enjoyable, just like Don Quijote or any other book that is well written.

— PewDiePie