Farley was 33 years old at the time of his death.
"20 years ago today," Spade wrote on Twitter, along with a photo of Farley.
Farley's best-known "SNL" characters often played on Farley's size -- he was well over 200 pounds -- and his manic, raging energy while also suggesting an underlying sensitivity.
Among the best-known of those characters were Weekend Update commentator Bennett Brauer; over-the-top motivational speaker Matt Foley, who was constantly reminding people he lived in a van down by the river; a teen girl who worked at the Gap; one of the Bill Swerski superfans whose catchphrase was "da Bears!"; and a shirtless Chippendales dancer in a bit that paired him with buff guest host Patrick Swayze.
After his "SNL" stint, which ran from 1990 to 1995, Farley starred in two films with fellow Spade -- "Tommy Boy" and "Black Sheep" -- and the solo-starring vehicle "Beverly Hill Ninja," before his death on Dec. 18, 1997 at his apartment in Chicago.