When the T.C.R.I. building had self-destructed, one of the Utroms, Dr. X, did not make it to the Transmat Device in time and was left behind in the wreckage of the building. Leatherhead found Dr. X and looked after her in the following years. Dr. X met Leonardo and Michelangelo prior to the testing of Leatherhead's second Transmat Device that led to a second Triceraton invasion (TMNT Vol. 3, #19). Dr. X presumably helped Leatherhead construct his two Transmat devices, though was not seen when Leatherhead recruited members of the Foot and the turtles to finish up the first Transmat Device he created (TMNT Vol. 1, #45), (TMNT Vol. 3, #19). Dr. X, with Donatello's help, constructed an android exoskeleton for herself (TMNT Vol. 3, #23).