In 2370, Lt. Commander Data began to have unusual nightmares when using his "dreaming" program. After a series of incidents, culminating in Data's stabbing attack on Counselor Deanna Troi, it became clear that he was subconsciously detecting interphasic organisms, which were extracting and consuming cellular peptides from crew members. If Data had been unable to discover a method of killing these organisms, the loss of these peptides would have ultimately proven fatal.
One of Data's dreams involved his cutting into Troi as a "cellular peptide cake... with mint frosting". He also saw Beverly Crusher drinking something from Riker's head through a straw. (TNG: "Phantasms")