Richard Nixon
Richard Nixon (1913-1994) was President of the United States from 1969 to 1974. He was criticized for his role in the Vietnam War and forced to resign because he masterminded a burglary in the headquarters of the Democratic Party in the Watergate Hotel in Washington in 1972. Nixon was the first American President who resigned from office.
References
Mentioned on Roxy & Elsewhere in the song Oh No after the line "the words from your lips", where Zappa adds "I'm not a crook", the infamous defense of Nixon during the Watergate affair. During the intro to Be-Bop Tango Zappa talks about "the old days" and concludes: "Well those days are probably gone for ever, unless Nixon is gonna bring them back a little bit later."
In Titties 'n Beer The Devil mentions: "You should have seen some of the souls I've had. Well, there was Milhouse Nixon and Agnew too. And both of those suckers were worse than you!"
Nixon is also the main target in the song: Dickie's Such An Asshole.