ALF names his dummy Paul. "Paul" and "Son of a Paul" are derogatory terms on Melmac.
"Son of a Paul" is a derogatory term of insult used on Melmac. (see Paul).
ALF decides to name his ventriloquist dummy Paul because it is one of the worst insults you can inflict on someone on Melmac. ALF even said that one time he called a guy Paul, ALF ended up in 14 stitches.