Blobboid is a superhero Turtle from an alternate reality, where he is Michelangelo's counterpart. He has the power to morph his body into a stream of liquid; even when solid, his body is constantly covered in slime. He also has limited shapeshifting powers. He appears in the 2003 series episode, Reality Check.
He is much more serious than Mikey and has very little humor.
Along with his brothers, Blobboid was once trained by Sliver until their master became evil.
Blobboid was first seen in a training simulator where he and his brothers - Griddex, Shellectro and Graviturtle - were battling holographic robot monsters. When interrupted by Michelangelo, Blobboid was surprised by the sudden appearance of a new Turtle, and unsure what he was talking about.
Michelangelo soon discerns that the Super Turtles are alternate versions of himself and his brothers, but doesn't seem to recognize Blobboid as being another version of him. Blobboid opts not to enlighten him, for unknown reasons.
Before more could be learned about Michelangelo's plight, Mayor April O'Neil arrived with news that Sliver was preparing to annihilate all life on Earth with the Penultimate Nullificator. Blobboid and his brothers set out to stop their archenemy with Michelangelo in tow. Unfortunately, they were imprisoned in a cage of Utromidium, which nullified their powers.
Without superpowers to help them, Michelangelo used his wits instead. He claimed that in his universe, Splinter and the Turtles rule everything as a family. Sliver released Michelangelo out of curiosity and a desire to hear more, only for "Michelangelo" to reveal that he was actually a shape-shifted Blobboid all along, and was easily able to free his brothers.
Unfortunately, in the fight that ensued, Blobboid had limited success against Sliver, as he had mastery of all the superpowers these Turtles had. Eventually Michelangelo was able to trap Sliver inside the cage, but with only seconds left before the Penultimate Nullificator was to go off. Shellectro reprogrammed the device to only destroy the tower they were standing in, and flew away with Blobboid before the entire tower was destroyed.
Later he was present when a statue of the "Turtle Titan" was erected.