|Behind the scenes|
Hot Dog (5.07)
Who Needs You (8.09)
Fenton is a recurring character in That '70s Show. He is first seen working at the jewelry store where Eric goes to buy Donna's engagement ring. He appears in several later episodes and becomes the landlord for Fez and Kelso's (later Fez and Jackie's) apartment in seasons 7 and 8. His character is flamboyant and slightly inappropriate. Even though it is never explicitly stated that he is gay, it can be assumed because of his stereotypical personality and appearance.
Fez and Fenton are enemies throughout the entire series. In "No Quarter", Fez explains that the start of the feud "involved a half-off sale, a crowded parking lot and a pair of pants that made my ass look like an oil painting". Jim Rash, on his Reddit AMA, confirmed this is a more loosely explanation.
Eric bought Donna's engagement ring from Fenton and has no backstory between them until season 6 where they seem to dislike each other because of the ring and Eric not being able to pay for it. When they get into a fight (similar to how Fez and Fenton fight) they say sorry to each other afterwards which shows that they don't hate each other. He doesn't like Donna as much as he likes Jackie.