The end of the doodle plays off an episode called "The Arena."
The story revolves around Kirk and a creature called a Gorn locked in a battle to the death. The stakes are high, especially for that poor redshirt.
In both the episode and the doodle, Kirk manages to create gunpowder out of local materials and fashions a primitive cannon.
The episode credits Fredric Brown for coming up with the plot. However, according to fan site Memory Alpha, the Star Trek staff didn't intend to base "The Arena" on Brown's short story of the same name.
Star Trek writer "Gene L. Coon wrote his script as an original (over the course of a weekend), unaware of Brown's story, and only sought permission to 'adapt' the story after the slight similarities were pointed out to him," the fan site says. "Brown was more than happy to hear that Star Trek decided to use one of his stories, and probably never found out the real plot behind it."
