Throw It In - The beginning to "Chop Suey!" is three drumstick taps and the engineer's voice saying "We're rolling 'Suicide'," the track's working title.
What Could Have Been - System of a Down is the 2000's version of Soundgarden, in terms of a band that disbanded at roughly the height of its popularity. In many respects, rock music has still not fully recovered from SOAD's split. Rock radio fractured into a mix of post-grunge interchangables and Guns N' Roses imitators. The rise of Guitar Hero, coupled with the return or reforming of veteran bands that preceded SOAD (Metallica, Pearl Jam, Rage Against the Machine, Alice in Chains, Stone Temple Pilots, Soundgarden) just about saved the hard rock format from being wiped from the radio dial in the late 2000's.
In all fairness, they haven't permanently split up so much as taken a long hiatus, which ends (at the time of writing) this summer with their reunion tour. Fans can only hope this leads to new material, but there hasn't been mention of this from the band.
There's also a LOT of material that never got officially released by the band, mostly appearing on file-sharing networks and bootleg albums. As System Of A Down took a lot of time between albums (three between the self-titled and Toxicity, four between that and Mesmerize/Hypnotize), it makes one wonder if they had other albums planned during those times.