NickVerse (Animated)

Just as the title says, this universe is comprised of animated shows of which aired on Nickelodeon and NickToons. Unlike most connected universes, this universe is technically more like a connected plane of existence of which all the shows share the same canon. This plane of existence may technically connect to the live-action NickVerse, which you can see here.

Shows part of this universe
The Loud House

The Casagrandes

Rugrats

Angelica and Susie's Preschool Daze

All Grown Up

The Wild Thornberries

Avatar The Last Airbender

The Legend of Korra

Hey Arnold!

Invader Zim

Jimmy Neutron

SpongeBob Squarepants

Blue's Clues

Kamp Koral

Shows in the same canon/plane of existence
The Fairly OddParents

Danny Phantom

Bunsen is a Beast

Tuff Puppy

Connection to the live-action universe
Big Time Rush