WMG / Pepper Ann

Pepper Ann takes place in the same universe as Doug
The two premises are similar, geeky middle schoolers who want to be cool and accepted. The animation styles and character designs are somewhat similar, and going by the theory that Bluffington is polluted in the Doug WMG page, that's why everyone on Pepper Ann is normal looking.

Pepper Ann and Codename: Kids Next Door share a universe as well
The art styles are nearly alike and they seem to share background characters.
  • ^^^^^^^
Related to the above
Pepper Ann could be the story of some of the "normal" kids/adults/teens in the Verse. People who don't know about/ don't participate in the KND vs Adult vs Teen conflict.