At around 8:41, Fez says, "Oh, to be a working stiff" in response to Kelso saying he's tired after "working all day". Laura Prepon (Donna) laughs. Donna wasn't around when Kelso decided to make a donation to the sperm bank, but the guys probably told her about it so that she knew what Fez meant.
This episode takes place in February 1978. Eric makes a reference to Battlestar Galactica which didn't debut until the following September.