zebra cum
Any liquid or gel of somehow questionable origin.  Phrase is usually delivered in a very excited or very deadpan voice.  It comes from a Lewis Black comedy routine:

"You ever read the ingredients in sunblock? I’ve never seen those words anywhere. You don’t even know what you’re putting on your face, do you? You go, “Oh no, the sun’s out!” It could be zebra cum; you don’t know. You may not like that joke, but you don’t know."
Joe: I found this unopened bottle without a label down by the river.
Bob: It could be zebra cum; you don't know!

Alison: How do they make this liquid makeup?
Jane: Zebra cum.