President Obama:  "Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan and everything in between.  But he was one of a kind.


"He arrived in our lives an alien . . . but he ended up touching every element of the human spirit."


Steve Martin:  "I could not be more stunned by the loss of Robin Williams, mensch, great talent, acting partner, genuine soul."


Robin's "Mrs. Doubtfire" daughter Mara Wilson:  "Very sad, very upset, very glad I did not have to hear about this though Twitter.  Probably going to be taking some time off it for a while."


Kevin Spacey:  "Robin Williams made the world laugh & think.  I will remember & honor that.  A great man, artist and friend.  I will miss him beyond measure."


Jason Alexander:  "Ah Robin, I'm so sorry the earth couldn't stay worthy of you.  Hope happiness awaits you."


Anna Kendrick:  "O Captain!  My Captain!  Rise up and hear the bells.  Rise up, for you the flag is flung, for you the bugle trills." (That's a "Dead Poets Society" reference.)


Lindsay Lohan:  "Mr. Williams visited me the first day of filming The Parent Trap.  I will never forget his kindness.  What an enormous loss.  My condolences."


Goldie Hawn:  "Oh Robin . . . Our hearts are broken.  Rest in peace darling.  We loved you."


Ellen DeGeneres:  "I can't believe the news about Robin Williams.  He gave so much to so many people.  I'm heartbroken."


Steve Carell:  "Robin Williams made the world a little bit better.  RIP."


John Mayer:  "The first thing I ever wanted to be when I grew up was Robin Williams' inhabiting of Popeye." 


Mindy Kaling:  "I am named after a character from a Robin Williams TV show when my parents still lived in Africa.  He meant so much, to so many, so far away."  "Mork & Mindy", obviously.


Mindy herself, Pam Dawber, said, quote, "I am completely and totally devastated.  What more can be said?"


"Night at the Museum" co-star Ben Stiller:  "A tweet cannot begin to describe the hugeness of Robin Williams heart and soul and talent. This is so sad."


Sarah Michelle Gellar just posted a montage of pictures of the two of them.  Probably from the set of their now-canceled sitcom"The Crazy Ones".