Early in the song, I hear super heavy pitch correction and the band-limiting on the EQ to give it a soft telephone effect.
Late in the song, there's some really weird stuff going on. The basis of it is using any plugin that can down-pitch sound an octave. But there are other artifacts that are trickier. It sounds like some of the things that happen when you start messing around in PrimalTap and Little AltarBoy (both plugins by SoundToys).
