There's a special reason why there's three sonic cartoons. Long John Baldry, the voice of Dr. Robotnik on the very hilarious Adventures Of Sonic cartoon, has died. All three of these cartoons contain clips from the show that were put together to make a (somewhat) coherent cartoon. The third one contains clips from the "serious" cartoon, but also more clips of Baldry's very funny Robotnik voice.
The cartoon that started this mess!
We've found some cool stuff in the woods. Now it's time for you to pinkie swear you won't tell mom and dad.
There's a Brainiac. He's not THE Brainiac. However, he's one aspect of Brainiac. Or maybe there's supposed to be a different Brainiac in every universe and they're all cosmically connected, presumably via their brains. Either way, I think this particular Brainiac is the boss Brainiac.
I highly recommend Windows 10 With Mouse + Keyboard Support Edition
Shmorky's Flash Tub. A collection of Flash cartoons and shorts, all crammed into neat little Flash Tub packages!