Pell Underhill was a 22nd century physicist who, according to Data, "conjectured that a major disruption in time-continuity could be compensated for by trillions of counter reactions."

In an attempt to deceive the crew, Data formulated a hypothesis, using Underhill as a reference, to explain why Doctor Crusher's mosses displayed an unusual amount of growth after a trip through a Paxan wormhole. While it was pointed out that Underhill's theories were with regards of energy, Data attempted to further explain his hypothesis that "it was possible that the phenomenon could occur in matter at much higher levels of organization. Given the proper conditions."

After Data was excused from the meeting, Geordi La Forge described Data's hypothesis as completely implausible, based on Underhill's theories, further explaining that he was "honestly amazed that [Data] even proposed it." (TNG: "Clues")