8. Samurai Jack and the Powerpuff Girls' horrifying secret crossover
Along with Dexter's Laboratory, the Powerpuff Girls and Samurai Jack were creations of animation mastermind Genndy Tartakovsky, and as such are often taken together as a bright spot in Cartoon Network's catalogue. Winks or nods between the shows might seem welcome and even expected, but any such easter eggs would have some dire implications.
As you may remember, Samurai Jack revolves around a warrior who is banished to the future by a demon named Aku. In the very first episode, we see a post-apocalyptic cityscape...
...that bears an uncanny resemblance to Townsville. As in, the city that the Powerpuff Girls call home.
If you think that's too ambiguous, Jack passes an old sign for Talking Dog Dog Food...
...which is more or less the exact same sign seen previously in Townsville.
It's all but confirmed: Samurai Jack and the Powerpuff Girls take place in the same universe. So what? Well, it's actually fucking terrifying.
Judging by what we're seeing, an unknown calamity hit the city right around the time that the Powerpuff Girls were active. All the buildings look like they're from roughtly the same era. Even that billboard remained up. We can only assume that something awful happened, something that the girls couldn't stop. Maybe Aku teamed up with Mojo Jojo and laid waste to everything. Maybe there was a mass exodus of people sick of giant monster attacks on a bi-weekly basis.
We don't see Blossom, Bubbles or Buttercup in any fashion during Samurai Jack; given the evidence, our best guess has to be that three five year-olds died at the hands of an immortal demon. All in the name of a neat easter egg.