Obsession

"Monsters come in many forms. You know the greatest monster of them all, Jim? Guilt." - McCoy to Kirk

"Intuition, however illogical, Mister Spock, is recognized as a command prerogative." - Kirk to Spock

"You know, self-pity's a terrible first course. Why don't you try the soup instead?" - Chapel to Garrovick

"Crazy way to travel! Spreading a man's molecules all over the universe!" - McCoy to Spock; on the transporter

Scotty : "Captain, thank heaven!"
Spock : "Mr Scott, there was no deity involved. It was my cross-circuiting to B that recovered them."
McCoy : "Well then, thank pictchforks and pointed ears."

People :

Spock, Leonard H. McCoy, Montgomery Scott