Before turning into a Mantis-person, Harold presumably looked like a regular human. He had black hair, a black moustache, had large front teeth and wore a blue suit with a white shirt and a brown tie to work.
As a mantis, he had his previous human-face stretched out over his head, two large yellow eyes of different sizes, two antennas, and large mantis-arms coming out of what was his human shoulders. He still had his human torso over his body, but his lower body was no longer covered in anything human, only mantis. His wings came out from under his suit.
Harold worked at Channel 58 for its breaking news update, which interferred with Summer watching Pregnant Baby. He and his co-host reported that Morty's whereabouts were still unknown before expressing their "love" for him, which resulted in a fight between them.
Harold's replacement version is assumed to have remained human, as the originals Rick and Morty have managed to ward off the disaster.