Similar to some humans, could there be any evil genius animals or insects that plot to take over the world? ~

"The ants are amassing an army and they've
  already got us outnumbered a million to one!"

None have the brain power. We'd have to wipe ourselves out first.

Roaches don't have a plot to take over the world, they'll just wait until the world (we) destroys itself.

Cockroaches will inherit the earth
It is popularly suggested that cockroaches will "inherit the earth" if humanity destroys itself in a nuclear war. Cockroaches do indeed have a much higher radiation resistance than vertebrates, with the lethal dose perhaps six to 15 times that for humans.  -wiki

If you've ever had a cat, you'd know the answer.