He originally was an odd-looking man with bluish skin, a goatee, and black hair kept long and messy. Also, he had overgrown, yellowed fingernails and rotten teeth. As of Ben 10 vs. the Negative 10: Part 1, however, he's now an insect, with a green exoskeleton, yellow eye stalks, antennas and wings on his back.
Powers and Abilities
Clancy was first seen with the ability to talk to and control any type of insect, though he can do this with any animal.
His new insect form has sharp claws, a durable exoskeleton as well as the ability to fly. He can travel undetected in a cloud of bugs, and can spew living insects from his mouth. He is a dangerous combatant with arthropods proportionate speed, strength and durability.
He used to live at 8610 Chester Street, an apartment that was built by his grandfather long ago. When Council woman Liang attempts to redevelop the area, he learns that his residential area must be torn down to successfully finish the project.
He decides to take action and tries to scare the construction workers away. When he finds out that it was the Councilwoman who ordered the demolition, he intends to feed her to his insects, but Four Arms is able to come to the rescue.
Sending fire ants to attack Four Arms, his attempt to save his home fails as Four Arms crashes into several support beams; causing the old house to collapse in on itself. Now homeless, Clancy plans to get his revenge against the people who took his home through the idea of destroying the whole city by means of a nuclear meltdown, with him surviving the blast with an armor made of cockroaches.
He is stopped by Heatblast (with his powers reversed due to Ben's cold), and is frozen in place to be carted away by the authorities. He manages to thaw out and escape, and soon decides to take revenge on the Tennysons for destroying his home and ruining his vengeance on the city. Luckily, Grandpa Max's San Ju Yen Pien medicine overrides Clancy's control over his insects and Max delivers the final blow to knock him out once and for all.
Later on, Clancy becomes a part of the Negative 10, although his appearance drastically changes. He appears to have mutated into a bug-like creature similar to a praying mantis; it's implied Dr. Animo had a hand in this.
In Ben 10: Protector of Earth, he appears as a mini-boss for the south-east/Bayou level, working for Dr. Animo. He appears in his unmutated form though retains his ability to travel in a cloud of insects. After Ben defeats him, he's interrogated for the location of the kidnapped Gwen though he provides no useful information other than Animo is plotting to turn Gwen into one of his mutated monsters.
In the fourth season of the original series in Ben 10: Secret of The Omnitrix trivia, it is revealed that Clancy does have the power to control animals mentally, though he only uses Arthropods because of the bond he developed with them.
He seems to share some similarities with the Totally Spies character Max Exterminus.
His control over insects mimics that of Shino Aburame from the Naruto franchise, only that the insects seemingly live inside of Clancy's clothing instead of his body.