Gus is a Russian repairman who was first seen in the episode Work Order where he was sent to repair the penguin habitat. The penguins try to stop him from digging into their antimatter fusion reactor core using a variety of traps. He remains undeterred, though the penguins do stop him from breaching the core by building a duplicate of the zoo so Gus thought he had completed the job.
He was also in Kanga Management telling Alice that he'll fix Leonard's habitat. In The Big Move, he tried to help Alice and Pervis Mcslade get in the zoo when the gate was locked. He also appeared in Love Takes Flightless fixing the hole that the penguins made during one of their burrowing missions and added a water fountain.
Gus is extremely determined to finish any job, even if there is fire, snakes, earthquakes, or cold. He isn't lazy and doesn't like taking the easy way out. He is extremely strong, able to break the floor of the penguins' habitat with a single punch.
He also has a rather entertaining tendency to call his biceps 'the boys', referring to them as though they were separate entities in themselves. This is best displayed when he tells Alice that 'he and the boys' are going to start work immediately.