 When Helena reaches for the copy of "The Complete History of  Everything" in the library, the book directly beside it is entitled  "Muppets in Space," using the font from _"Farscape" (1999)_ (qv).  "Farscape" is another Jim Henson Company production set in space.  This joke is often mistaken for _Muppets from Space (1999)_ (qv),  the 1999 film.