The tightly-constrained budget of The Original Series seldom left money for off-duty civilian costumes for the principal cast. That's one reason why everyone seemed to wear their uniforms nearly 24/7. One exception to this was Captain Kirk, who had a nifty informal wraparound shirt. This style was first seen in "The Enemy Within" from Star Trek: The Original Series, where it helped viewers tell the difference between the two versions of Captain Kirk. The good captain also wore this style of shirt in "The Trouble With Tribbles" from Star Trek: The Original Series. These unfinished versions of the wraparound suggest that it would have made an appearance in Star Trek: Phase II, as well.