He's a hulking Caucasian male with short brown hair.
He's dedicated to his work, and was rather thoughtful when telling Scooby-Doo to give him a call if he ever needed a janitor. He was so dedicated to the bank that he followed the trail of the sludge monster that robbed it.
A Pup Named Scooby-Doo
His boss, Mr. Buckston, dressed up as the Sludge Monster from the Earth's Core so he could steal all the money and frame it on him. When the Scooby gang was on trail of the Sludge Monster at the bank, only to then find Mr. Williams, it made him a suspect. Given the rough appearance of Mr. Williams, as well as the temptation of being around large amounts of money, it made sense that he would try to rob the bank as the Sludge Monster. However, Mr. Williams was found innocent and thanked the gang for exonerating him. (The Sludge Monster From The Earth's Core)