When does Pinky and the Brain return?

The characters first appeared in 1993 as a recurring segment on the animated television series Animaniacs. Pinky and The Brain are genetically enhanced laboratory mice who reside in a cage in the Acme Labs research facility. The Brain is highly intelligent, self-centered and scheming, while Pinky is good-natured but feeble-minded. In each episode, The Brain devises a new plan to take over the world which ends in failure.
There is very little continuity between Pinky and the Brain episodes, outside of the common fixtures of the two mice. The bulk of every episode involves one of Brain's plans for world domination with Pinky's assistance and the ultimate failure of that plan.