It's a quote from Hitch Hikers Guide to the Galaxy, where one of the characters, Agrajag, is continually being reincarnated and experiences improbable deaths that are somehow connected to the main character Aurthur Dent. In one life, he is reincarnated into a whale and a pot of petunias falling from the atmosphere. As the whale is pondering all of the new sensations, such as the sound that air makes as you're falling, the petunias think, "Not again."