Lard Lad came to life (along with many other advertisements in Springfield) after a mysterious storm passed over Springfield and the advertisements were struck by lightning. Coincidentally, Homer had just stolen Lard Lad's colossal donut, so on coming to life, Lard Lad went after Homer to get his donut back. He then joined in with the other advertisements in trashing the town, hitting things with his donut. He and the other advertisements were defeated when Lisa (with help from Paul Anka) got the townspeople to stop looking at them. However, it took some extra effort to make Homer quit looking at Lard Lad.
Do not feed the Lard Lad, no matter how much he may attempt to attract your attention.