Title text: Sn = tin
In reality, Snapple is a brand of tea and juice based beverages whose name is based on a carbonated apple juice they once produced ("snappy apple"). The joke in this comic is pretty self-explanatory; especially given that the image text continues the trend in early xkcd comics of explaining the joke. Tin is a metallic element whose abbreviation on the periodic table is "Sn" (as the Latin word for tin is "stannum"). Thus, the apple is a "Sn-apple."
The fourth panel is a silent wide shot, perhaps suggesting the joke was met with silence as a weak joke. As a meta joke, the final panel might jokingly suggest that the silence is because those unfamiliar with the table of elements don't get the joke.
- This one is entirely James' fault.
- [Two guys are standing and talking.]
- Cueball: Here, take a bite of this Snapple.
- Guy: food!
- [Guy takes a bite.]
- Guy: Ow! What is this?
- Cueball: It's an apple infused with tin.
- [The two guys continue to stand as if frozen.]
- Those of you who know your periodic table should be laughing right about now.
- This is another early xkcd comic in which Cueball characters are drawn in some panels with faces.
- This is the seventeenth comic originally posted to LiveJournal. The previous was 17: What If. The next was 19: George Clinton.