The world was watching - and tweeting - as Donald Trump and Hillary Clinton clashed face-to-face for the first time.
"Maybe we should try 4 years without a president?" - US comedian and actor Jim Gaffigan.
"A highly-rated and POPULAR TV star is on TV right now next to a smart person who probably doesn't watch much TV." - director Michael Moore.
"She's smiling with ease cause #shesgotthis #ImWithHer" - singer Katy Perry.
"Hillary wants us to go to her website to check her facts. THAT'S WHAT I AM HERE FOR HILLARY. I give her website 'Pants on Fire'" - Former Republican presidential candidate Dr Rand Paul.
"Trump cares about your city if he has property there. Hillary cares about your city because YOU are there." - YouTube star Tyler Oakley.
"To keep up with Trump's b******* they had to outsource fact-checking to China. Sad." - US comedian Bill Maher.
"Clinton understands systemic racism is nuanced & needs to be tackled on every level. Trump wants to paint himself as a white (orange) savior" - Hollywood actress and writer Lena Dunham.
"The arrogance of this man is stunning in its brazenness, and sad in its utter lack of humanity." - Star Trek actor George Takei.
"The way Trump's sentences connect one to the next is very Human Centipede. I've never in my lifetime seen babbling incoherence on a Presidential debate stage like Trump is displaying tonight. I'm in a nightmare." - Family Guy creator and actor Seth MacFarlane.
"Trump's promoting his new hotel at a debate." - US comedian Patton Oswalt.
"Trump has 1. Basically admitted he pays no taxes 2. admitted he stiffs people 3. insists this is 'smart' - Adam Servianski, editor of The Atlantic.
"How could any half sane person even consider voting for this giant narcissist? He is an out and out liar and a shyster. Yes, you Trump" - political commentator and former Conservative candidate Iain Dale.
"Hillary Clinton belongs in the White House. Donald Trump belongs on my show" - US chat show host Jerry Springer.