Did they ever give a reason for the title "Spaghetti Incident"? I thought Slash did in his book, but I don't recall for certian.
The title is an inside-joke referring to a food fight between Axl Rose and Steven Adler involving spaghetti. Much was made of this food fight during Adler's resolution lawsuit with the band in 1993, in which Adler's attorney referred to it as "the Spaghetti Incident". The meaning was explained by drummer Matt Sorum in a 1994 interview with Much Music and confirmed by Slash in his autobiography, Slash.
The title may also be a play on the title of the 1991 film The Linguini Incident.
During a discussion between Rose, Slash and the album's cover designer in the "Making of Estranged" video, it is made clear that the correct form of the title is within quotation marks and with a question mark.