Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

Two unicorns are shown in an intimate encounter. One unicorn exclaims "Oh God, baby, that is so hot, so hot!" while the other says "Oh God, oh God... I'm gonna..." and a third voice (or the same unicorn) shouts "Pull out, Steve! Pull out!" The next panel reveals the aftermath: a rainbow arcing across the sky, emanating from the unicorns' location. The final panel shows the unicorns looking somewhat embarrassed, with the implication that the rainbow is a, shall we say, biological byproduct of unicorn romance.

The comic provides an irreverent origin story for rainbows. In popular culture, unicorns are often associated with rainbows, sparkles, and general whimsy. This comic takes that innocent association and gives it a decidedly adult explanation: rainbows are what happen when unicorns fail to practice safe... unicorn activities.

The Humor

The humor is pure shock comedy, taking the most saccharine and child-friendly mythological imagery -- unicorns and rainbows -- and recasting it in explicitly sexual terms. The phrase "Pull out, Steve!" grounds the fantasy scenario in mundane human relationship dynamics, which makes it funnier. The visual punchline of the rainbow appearing as a consequence of the unicorns' tryst is simultaneously crude and oddly logical within the comic's internal mythology. The name "Steve" for a unicorn also adds an incongruously ordinary touch to an otherwise magical creature.