1 Mike: What is this strange painting on the wall?
2 Lucas: Oh my god! It’s the fresco from the entrance of the Tomb of Horrors! We’re in the Tomb of Horrors!!
3 Dustin: But... that’s a D&D dungeon. Who would build an actual D&D dungeon in real life?
4 Mike: Bigger nerds than us.
4 Dustin: Oh my...

Those who are familiar with the infamous Tomb of Horrors will recognise the fresco on the wall shown here. The original adventure module came with a separate booklet of illustrations, intended to be shown to the players at various specific points in the adventure, to illustrate and evoke the atmosphere of the tomb. It's a real work of art.

The image is reproduced here in part, at low resolution, partially blurred and obscured, and as a subject for parody under the doctrine of Fair Use.

Oh, and I hadn't intended it at the time because I often don't plan my stories out this far in advance, but it turns out this strip was some seriously clever foreshadowing.