Guillermo is a Latino man hired by Jonathan Weed of Happy-Go-Lucky Toy Factory as a ringer to beat the rival toy company at the annual softball game in "A Hero Sits Next Door". He is rushed to the hospital when Peter Griffin accidentally hits him with a pitch during practice.
It is clear in "A Hero Sits Next Door" that Mr. Weed is sexually attracted to Guillermo, and it is suggested that he is also gay as Peter later describes a scene including Guillermo and Mr. Weed that is similar to homosexual intercourse.
He also has a cameo appearance in "Fifteen Minutes of Shame", sitting in the audience of Diane! and shares a table with Bruce, Jasper, and Ricardo in the afterparty of Stewie Griffin: The Untold Story.