Apologies if this has already been discussed before, when I look it up on google there's no results, so..
I have Renpy on my desktop, and a picture of Sayori on my desktop, and a few weeks ago I realized the looked pretty similar.
Now, I'm not saying Dan Salvato did this on purpose (knowing him though, he could have). He probably just had the Renpy mascot's image repressed in his mind when thinking about how Sayori looked (after all, if you didn't already know, DDLC was made in Renpy.)
I don't know, what do you all think?