“Joe Frazier is so ugly that when he cries, the tears turn around and go down the back of his head.”
As quoted at "Ali's Quotes" at BBC Sport : Boxing (17 January 2007) http://news2.thdo.bbc.co.uk/sport1/hi/boxing/6267397.stm
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Muhammad Ali 100
African American boxer, philanthropist and activist 1942–2016Related quotes

“When danger reared its ugly head,
He bravely turned his tail and fled.”
Source: Monty Python and the Holy Grail (Book): Mønti Pythøn Ik Den Hølie Gräilen

“Man cries, his tears dry up and run out. So he becomes a devil, reduced to a monster.”

Source: No One Belongs Here More Than You

“Go back! Turn around! Stop killing my people!”
These two statements are frequently attributed to Tank Man on the Internet. While it seems clear from the footage that some communication occurred between Tank Man and the people in the front tank, no confirmation has ever been made as to what was actually spoken.
Misattributed
It's just flat."
Comedy Central Presents, S01E06: Mitch Hedberg https://www.youtube.com/watch?v=iAHiHJ2AhYE&feature=youtu.be (5 January 1999)

The Soldier's Funeral from The London Literary Gazette (16th November 1822)
The Improvisatrice (1824)