The Simpsons: 19x17

Apocalypse Cow

Bart joins the 4-H club and falls in love with a cow named Lou, but when he finds out that Lou is destined for the slaughterhouse Bart gives the cow to Mary, a fellow 4-H member, and her father mistakes the cow for a dowry. Homer and Marge come to the rescue to try and free Bart from his marriage agreement.