Krusty was paid to do a personal appearance (Bart’s party?) so he aired a re-run of his show on the assumption that no one would notice. The joke is that the episode he airs just happens to break the news about an historical event (Falklands war).

I repeat - the Falklands have just been invaded! The disputed islands lie here, off the coast of Argentina.

I always love it when Krusty gets all serious about world events on his kid’s show.

The episode is Burns’s Heir.