The "spirit dice" Darryl gives to Roxie are customized versions of some of the common role-playing game (RPG) non-cubic dice: an eight-sided die (d8, an octahedron with triangular faces), a ten-sided die (d10, a pentagonal trapezohedron with kite-like faces) and a 12-sided die (d12, dodecahedron, with pentagonal faces). Usually, in RPGs, the dice faces have sequential numbers, but Darryl's dice have "mystic" symbols instead.