Complex sentence: "The Santa Simulation" marks the second appearance of "Dungeons & Dragons" in a "Big Bang Theory" plot, with it appearing earlier in season 5's "The Wiggly Finger Catalyst".
Split into simpler sentences: The Santa Simulation marks the second appearance of "Dungeons & Dragons"in a "Big Bang Theory"plot. It previously appeared in season 5's "The Wiggly Finger Catalyst".