Star Trek: 10 Alien Encounters Before First Contact
9. Quinn - Death Wish
The Q are ageless, omnipotent beings, who generally tend to remain above it all. By this, we mean they're so utterly bored of existence that they may as well be monuments to their own technological and historical advancement. Well, that is, until Quinn was freed from his meteoric prison.
This errant Q had been shoved inside that rock 'for his own good'. Having introduced the idea of mortality to the continuum, he was silenced before these thoughts could infect other, 'good' Q. He had also taken more of a direct role in influencing history.
At his trial aboard Voyager, three witnesses were summoned to attest to his good works. Sir Isaac Newton recognised him as a man who had been sitting against a tree, jostling it as he rose - causing the apple to fall. Maury Ginsberg was grateful to him for giving him a ride to Woodstock, ensuring he was present to fix a sound issue that could have derailed the entire concert.
Lastly, a certain William T. Riker claimed not to know him - until he saw a sketch that saw Quinn standing alongside Thaddeus Riker, the commander's ancestor. Quinn had saved the man's life, thus ensuring the continuation of Riker's line, indirectly saving humanity from the Borg.
Not every alien encounter has been destructive, nor have they been particularly open. There is a very funny idea in that the Q have secretly been influencing history in their own, strange way.