pepe the frog
"Feels good, man."
Pepe is a cartoon anthropomorphic frog, originally created by artist Matt Furie for the comic Boy's Club in 2005, but that first gained notoriety as a meme on 4chan in 2008 with many different meanings -- initially as its original incarnation for something that feels good, then turned into a symbol of negativity and depression around 2009 when his catchphrase was turned into "Feels bad man", then turned into a symbol of crippling depression around 2011, then turned into a symbol of hate against normal people around 2013, then turned into a symbol of Donald Trump supporters, white nationalism and the alt-right movement in the wake of the 2016 presidential elections.
In 2017, Matt Furie attempted to thwart the use of Pepe as an alt-right mascot by enforcing DMCA takedowns on notorious white nationalist websites.