Overview 
      
        
          | Production number | 
          42 | 
         
        
          | Air date | 
          Dec 29th, 1967 | 
         
        
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          | Director | 
          Joseph Pevney | 
         
        
          | Teleplay | 
          David Gerrold | 
         
       
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      - Story
 
      
        
          | Stardate 4523.3 | 
         
        
          | When the Enterprise and station K-7 are crawling with high-producing tribbles, a
          Klingon spy can be disclosed. | 
         
       
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      - Guest Cast
 
      
        
          | Stanley Adams | 
          Cyrano Jones | 
         
        
          | William Schallert | 
          Nilz Baris | 
         
        
          | William Campbell | 
          Captain Koloth | 
         
        
          | Michael Pataki | 
          Korax | 
         
        
          | Charlie Brill | 
          Arne Darvin | 
         
        
          | Whit Bissel | 
          Mr. Lurry | 
         
       
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      - Rating
 
      
        
     
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