Chameleonic fluctuation
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Two different exteriors of the Doctor's TARDIS. (TV: Twice Upon a Time [+]Loading...["Twice Upon a Time (TV story)"])
Chameleonic fluctuation was, according to the Seventh Doctor, a property of the chameleon circuit responsible for the TARDIS exterior subtly changing over many years whilst it remained locked in the form of a police box. (PROSE: St Anthony's Fire [+]Loading...["St Anthony's Fire (novel)"])