My Favorite Martian (1963) : 1x4

Martin reads about a $2 billion American space program, a program he knows is doomed for failure. Not wanting to see the American government waste $2 billion, Tim writes himself a fake letter to the newspaper which includes Martin's nighttime musings; Tim thinks Martin's mumblings are key to the flaw in the space program. Based on the fake letter, Tim writes a newspaper story criticizing the wasted $2 billion. Tim's masquerade is uncovered by the government, agents for whom think he's a spy working for the Russians. Tim is questioned under a lie detector, and he fails miserably when it comes to questions about Martin. So the agents call in Martin, the agents who question him under the lie detector, under hypnosis, and through brainwashing. Martin overcomes each, to him, primitive method. But he can't overcome the truth serum, and he spills the beans about being a Martian. It isn't until then that the agents let Tim and Martin go. They figure that Martin is crazy and delusional, which is causing stress on Tim which in turn made him write the letter.