The Drip is a mutant that was accidentally created by Donatello whilst attempting to synthesize a Retro-Mutagen. Donatello had a hypothesis that the electrolytes in Michelangelo's sports drink, "Refresh-aid", would help stabilize the Retro-Mutagen. However, it only served to create a tiny living red drop of liquid. Donatello put The Drip in a jar and went to sleep, but found in the morning that it was dehydrating. Donatello poured a drop of water on it and it perked back up.
That night while everyone was sleeping, The Drip got out and suctioned out all of the water in a mug Michelangelo was drinking out of, then found the leaky faucet of a sink and went after it. Donatello woke up to find himself completely submerged in water.