Trivia: When Eddie is unsure of the year, Harry says, "it's 1985. Reagan is President." Eddie replies, "the actor?" This is the same response Doc Brown gave Marty McFly in "Back to the Future" when he asks Marty who the President in 1985 was. This episode aired less than 5 months after "Back to the Future" was released.
Trivia: In this episode, the rock star Eddie Devon is played by Michael Ross. Ross was the real-life husband of Markie Post, who plays Christine Sullivan.
Answer: Being declared legally dead is called "death in absentia", meaning there is no evidence of death (i.e. a body), but the individual is presumed dead. This can happen to anyone, not just MIA soldiers. If a spouse petitions the courts to grant a divorce on the presumption of death and all criteria are meet, they are legally divorced and free to remarry. The return of the presumed dead would not change the divorce ruling. However, if a spouse does not go through the legal steps prior to remarrying, then the return of the presumed dead spouse would nullify and void the 2nd marriage immediately (and the remarried spouse could face bigamy charges).
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