The condition is that it should work to invoke on a typical shell prompt and ideally say something funny or nonsensical.
curl -LOL http://example.com
curl -eats -wgets -breakfast http://example.com
curl -curl -curl -curl -eats -wget -For=breakfast http://example.com
curl -the -untergang: -is -close http://example.com
From Benjamin Marwell:
curl -JOLLY 30 https://example.com/file