A Pig Is a Boy Is a Dog - S4.E23

Brenda and Donna attend an animal rights rally, and are crestfallen when the university refuses to suspend animal testing. After Rocky dies of cancer, Brenda becomes involved with a small group of radicals. She serves as lookout when the group breaks into the university research building, and tries in vain to save Andrea's lab (which does not harm animals in its testing). Brenda is arrested. Kelly and Brandon are furious when Dylan refuses to fund Lucinda's film. He finally tells Kelly that Lucinda came on to him. Brandon breaks up with Lucinda, and Kelly confesses her kiss with Brandon. Dylan races over to the Walsh house to fight Brandon, but the tension is defused when he accidentally punches Steve.