Reddit user genghiskwanquer put together an animated short that showed Robin trying to get revenge on Batman for being slapped in a sequel to that viral 'Batman slaps Robin' meme that has become so popular for the last decade plus.
The meme originated around Christmastime 2008, with the original text being Robin asking Batman what his parents got him for Christmas and Batman responding by slapping Robin, screaming, "My parents are deeaaaaaaaad!" People were shocked at the fact that it is clearly actual Silver Age comic book artwork showing Batman slapping Robin, and the extra dialogue just adds to the joke.
The original panel (which is actually flipped from the original, so Batman is on the left side of the panel in the original) appeared in 1965's World's Finest Comics #153 by Edmond Hamilton, Curt Swan and George Klein. It was an "imaginary story" (basically DC's precursor to Marvel's What If...?) where Thomas Wayne was killed in Smallville instead of in Gotham City and Bruce Wayne assumes that Superboy did it, so he dedicates his life to killing Superboy.
At the same time, he also becomes Batman and fights crime in other ways and eventually takes on Robin as a partner, just like the regular continuity. However, when Robin discovers Batman's obsession with killing Superboy (now Superman), he tries to talk Batman out of it, but the unhinged Dark Knight slaps him and erases his memory of being Robin and sends him away. Batman succeeds in killing Superman, just as he learns that it was Lex Luthor who actually killed Thomas Wayne. What a bummer of an alternate reality.
In this animated sequel to the meme, though, Robin cries from the slap, but even as the tears are falling from his eyes, he begins to do one-handed push-ups to strengthen his slapping arm/hand. He then also does weight lifting with just the one arm/hand and begins practicing slapping wooden instruments with Batman's face on it. He finally is ready and confronts Batman and then slaps him and...it doesn't affect Batman at all and the cartoon ends with Batman's hand coming back towards Robin's face for another slap.
This matches that imaginary story in being a real bummer of an ending!
Source: Reddit