The biggest fail in TOS happens in the third season in the episode titled The Way to Eden. In it a group of space hippies take control of the USS Enterprise 1701 through the power of peace, love and good happiness stuff. Well, thats not entirely true. They do get uncool and heavy by sticking it to The Man, i.e. Kirk, calling him Herbert and stiff. Up your face, Kirk! Aside from that, they're sweet hearts. All snark aside, really think about this. The flagship of the Federation, manned by the best crew, is taken hostage by a group of no-shoe wearing space hippies. Really?!? Really! Ok, one of them is wearing thigh-high velvet boots, but theyre definitely space hippies. They even manage to get Spock to cut loose and sit in on their jam session, which serves as the big distraction for their coup. For a coldly logical Vulcan, Spock can rock the Vulcan Harp. Wow, man, like... far out! Maybe Space Hippies are far more deadly than their 60s bretheren, but thats not how they come across in the episode. Heres a video showing them in all their glorious ferocity: http://youtu.be/MRewcZXEMb8