Caspar Weinberger (1917-2006) was the American Secretary of Defence between 1981 and 1987. Portrayed with suspiciously shark-like features, he was one of Ronnie's more long-suffering aides, and was mostly in charge of making sure Ronnie never started any unsolicited wars whilst his back was turned.
As his job title suggests, "Cap" was in charge of the military and America's defence - no easy task under the rubbery warmonger Ronnie Reagan. Many sketches featured Caspar trying to talk Ronnie out of causing unintentional wars due to his sheer stupidity - Ronnie frequently comes close to causing war by making prank calls to Russia and and threatening to bomb Libya under the impression bombing the enemy worked in Vietnam and World War II. During any war America was already involved in, it would be Caspar's job to discuss plans of action with Ronnie - all of Ronnie's suggestions being just plain nonsensical. Names for the enemy in Libya for use in press material suggested by Ronnie included "Charlie" (used previously in Vietnam and Korea), "Jesus" and "Larry".
When seen communicating in England, however, Caspar is shown to be rather closed-minded and manipulative. Talking to George Younger about the two nations' "Special Relationship", he gets Younger to support Trident and the STI initiative without giving anything back to England whatsoever, claiming "that's what makes the relationship special".
Throughout his short appearance in the show, Caspar is voiced by John Sessions.
In the Audience with Ronald Reagan sketch an audience member asks him "How's your asshole?". Reagan then answers and replies by saying "Caspar Weinberger's doing just fine!".