"The Time Merchant", in which John signs away 5 years of his life in a contract with the titular time merchant.
How about the time merchant explaining that the faster a person moves, the more time they use up as a result? Think about that for a second. You could be burning up years of your time simply by being in a hurry to get something done faster.
When Robot is programmed to kill the Robinson Family and John shoots at him. The Robot dodges the shot, then turns slowly back to face John, as if it's glaring before saying its next line in such a cold tone.