Hey! I used to have that record! :^)
I'd have to give the award to Imaginarium, by Terry S. Taylor. If you've ever played Neverhood, that's the soundtrack. It's insane, but oh, so awesome. :^)
http://www.youtube.com/v/DXQ2lvgpHiE&hl=en_US&fs=1&
I always wondered who did the music for that. I thought Leon Redbone was involved with it for some reason...I think a reviewer mentioned it sounded like him on a couple of songs. And for a long time I loved just coming up with lyrics for what I thought it sounded like they were saying. Shame that the soundtrack's going for $50 on Amazon now, though.
As for absolute oddest CD I've personally listened to, I'd have to go with The Frogs, "My Daughter the Broad." If you don't know The Frogs...well, other than the album, I haven't really heard anything else by them, but apparently they used to tour with Smashing Pumpkins and wear bat-wing costumes. They are two incredibly weird guys that basically sit in a recording studio and just make up songs about the craziest, many times wildly offensive nonsense. I wouldn't say it's all necessarily good or funny (some of it is hysterical, though), but it definitely qualifies as insane.
For example, one of the songs, sung in the put-on voice of what I guess is an 85-year-old man, goes, "I'm sad because my goat just died todayyyy...I'm saaaaad, my goat just fell in the hayyyyyyyyy....HEY!"