Ronald Reagan (1911-2004) was the President of the United States of America between the years 1981 and 1989. Along with Margaret Thatcher and the Queen Elizabeth II, he is one of the show's most memorable characters.
Reagan, referred to in the show by his real-life nickname "Ronnie", was portrayed as a bumbling old fool who would declare war on any country he saw as a threat and would always need his trusty (if not often manipulative) aides to explain even the simplest commands. His occasional bursts of brilliance are hampered as his stupidity gets the better of him - he surprises his friends with news he has built a top-secret bomb-testing facility the Russians will never discover; the facility is located, of course, in his anus.
Without his aides, Ronnie was virtually useless; he even requires supervision to eat lest he eat from the fishbowl or jab himself in the face with a fork. Ronnie's aides often take advantage of his simple-mindedness and manipulate him into doing their bidding. Don Regan gets Ronnie to give him more taxpayer dollars to invade Russia by confusing Ronnie about the Domino Effect: He thinks Russia is trying to steal his toy dominoes. However, Ronnie's behaviour is more than enough punishment - he frequently comes close to causing nuclear war, for example in one episode Caspar Weinberger finds Ronnie making dirty noises down the phone linked directly to the Kremlin. Ronnie frequently confuses his aides' names and at some point merely resorts to calling all of them Larry.
Ronnie does show some independence however whenever he is seen alongside Margaret Thatcher. He frequently manipulates *her* into doing his bidding; in many episodes it is hinted the two have some kind of love interest. One of the more famous sketches highlighting this includes Ronnie and Maggie making out in airport, leading Ronnie to state "Fine woman. Pity I'm only screwing her country."
Chris Barrie voiced Ronnie during his time on the series.