junk
Explanation
The Joke
The comic explains that the solar system was once a huge mass of space junk, and over time most of it accreted into planets. However, a few planets kept some of that junk orbiting around them. One planet in particular -- Saturn -- kept the most junk and is considered the most beautiful planet of all. The final panel shows a woman in bed telling a man: "Just throw out your old power cords! You will never use them!" He responds indignantly, "I am Saturn, Jessica. Saturn."
The Humor
The comic draws a parallel between Saturn's famous rings (which are made of debris, ice, and rock -- essentially space junk) and the common human habit of hoarding old cables, power cords, and other useless items. The man uses Saturn as a justification for his hoarding: if the most beautiful planet in the solar system achieved its glory by holding onto its junk, then surely his collection of tangled power cords is similarly magnificent. The humor lies in the absurd grandiosity of comparing a messy cable drawer to one of the wonders of the solar system, while also making a surprisingly valid analogy -- Saturn really is celebrated precisely because it kept its debris rather than absorbing it cleanly.
References
Saturn's rings are composed primarily of ice particles, rocky debris, and dust, ranging in size from tiny grains to house-sized chunks. They are believed to be remnants of comets, asteroids, or moons that were broken apart by Saturn's gravity before they could be absorbed into the planet.