The Naked Time SEASON 1, EPISODE 04
Wiki Entry:
http://en.wikipedia.org/wiki/The_Naked_Time
This was a top episode - a strange disease infects the Enterprise, acting like a drug and supressing rational thought. It's also well known because of some of its imagery, specifically Sulu fencing topless and Spock struggling with emotional turmoil. We also have Nurse Chapel explicitly expressing her feelings to Spock for the first time. But ignoring that, a really well crafted, dramatic and engaging episode. Interestingly, I really thought the guy that first got the odd disease was a relatively famous actor - I actually thought he was a young Bradford Dillman - but he's not. I realised he was familiar to me because he pops up in another Star Trek episode called 'By Any Other Name' as a bad guy, and this particular episode is the one I've seen the most time (I used to own this episode on Super 8...anyone remember that?). This is the guy in question btw:
We also get a crewman I really liked and I think he appears in an episode or two more down the line: Kevin O'Rielly:
Anyway, imo this is the best episode so far.
STILL NO DEAD RED SHIRTS SO FAR!
To put it in my list of order of how much I liked it:
Top.-
The Naked Time (S1E04)
Charlie X (S1E02)
Where No Man Has Gone Before (S1E03)
The Man Trap (S1E01)