“Do you seriously entertain the idea that without the observer there is no reality?”
"On the Philosophical Problems in Quantizing Macroscopic Objects"(ca. 1962-1963) as quoted by Morinigo, Wagner, & Hatfield, Feynman Lectures on Gravitation (2002)
Context: This is all very confusing, especially when we consider that even though we may consistently consider ourselves to be the outside observer when we look at the rest of the world, the rest of the world is at the same time observing us, and that often we agree on what we see in each other. Does this then mean that my observations become real only when I observe an observer observing something as it happens? This is a horrible viewpoint. Do you seriously entertain the idea that without the observer there is no reality? Which observer? Any observer? Is a fly an observer? Is a star an observer? Was there no reality in the universe before 109 B. C. when life began? Or are you the observer? Then there is no reality to the world after you are dead? I know a number of otherwise respectable physicists who have bought life insurance.
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Richard Feynman 181
American theoretical physicist 1918–1988Related quotes

“Entertainment is all right, but entertainment with an idea behind it is much more important.”
On exposing antisemitism in Gentleman's Agreement. Gregory Peck: A Charmed Life by Lynn Haney (2003). page 148. ISBN 0786714735.
In a discussion thread https://www.lesswrong.com/posts/Q8jyAdRYbieK8PtfT/taking-ideas-seriously#Ym77AptKtD2h9bXXd on LessWrong, August 2010
Source: “Evolutionary Theory and Theological Ethics” (2012), p. 250
Source: Pictures from an Institution (1954) [novel], Ch. 4, p. 173

“Do you decide to observe? Or do you merely observe?”
5th Public Talk Saanen (26th July 1970); also in "Fear and Pleasure", The Collected Works, Vol. X
1970s
Context: Do you decide to observe? Or do you merely observe? Do you decide and say, "I am going to observe and learn"? For then there is the question: "Who is deciding?" Is it will that says, "I must"? And when it fails, it chastises itself further and says, "I must, must, must"; in that there is conflict; therefore the state of mind that has decided to observe is not observation at all. You are walking down the road, somebody passes you by, you observe and you may say to yourself, "How ugly he is; how he smells; I wish he would not do this or that". You are aware of your responses to that passer-by, you are aware that you are judging, condemning or justifying; you are observing. You do not say, "I must not judge, I must not justify". In being aware of your responses, there is no decision at all. You see somebody who insulted you yesterday. Immediately all your hackles are up, you become nervous or anxious, you begin to dislike; be aware of your dislike, be aware of all that, do not "decide" to be aware. Observe, and in that observation there is neither the "observer" nor the "observed" — there is only observation taking place. The "observer" exists only when you accumulate in the observation; when you say, "He is my friend because he has flattered me", or, "He is not my friend, because he has said something ugly about me, or something true which I do not like." That is accumulation through observation and that accumulation is the observer. When you observe without accumulation, then there is no judgement.

“Reality is in the observations, not in the electron.”
A summary of Heisenberg's view by Paul Davies in his introduction to Physics and Philosophy
Misattributed