An unexpected bottle of champagne is always welcome. One of my secret weekend vices is doing insanely difficult newspaper crosswords, and The Independent rewards winners with bubbly. Cheers!
Though SF-themed crosswords are quite common, few SF stories involve cruciverbalism. Evelyn E Smith's "BAXBR/DAXBR" is one, with a puzzle-obsessed protagonist who's so excited by fitting shiny new Martian words like baxbr and daxbr into crossword grids that he doesn't grasp their context, the planned Martian annihilation of our puny species. I know that feeling.
In Arthur Sellings's "One Across", the hapless hero solves a crossword with no diagram – slowly realizing the words connect in multiple dimensions. Across, down, through and out. Unfortunately, visualizing the fourth dimension sucks him into it (as so often happens in sf) and a terrible fate looms.... Clive Barker's "The Hellbound Heart" mentions a crossword that opens another dread portal.
Addicts automatically read words backwards, just in case. The city in Ursula Le Guin's "The Ones Who Walk Away from Omelas" was inspired by a Salem, Oregon roadsign. Under Milk Wood's fabulous Welsh town was originally Llareggub, later toned down to Llaregyb for sensitive BBC listeners. When Terry Pratchett invented the Discworld version of Wales, he followed Dylan Thomas's lead and called it Llamedos. Robert Heinlein's Tunnel in the Sky lays a trap with a dire warning against "stobor", which are not what smartarse readers expect. Obscure SF author Robert C Givins also wrote as Snivig C Trebor. Not a lot of people wanted to know that.
Backward-readers particularly love Edward P. Bradbury's Barbarians of Mars, an imitation Edgar Rice Burroughs adventure dotted with oddly familiar names: Drallab, Golana, S'sidla, Nosirrah, even K'cocroom. Yes, "Bradbury" was really Michael Moorcock. As a treat for SF fandom, he threw in the Flowers of Modnaf: "Their scent from here is pleasant, but when approached more closely it induces first a lethargy, then a creeping madness....."
Anagrams are stealthier and less obvious. Practically the only Star Wars trivia answer I know is that Lando Calrissian rearranges as Carolina Islands. Master parodist John Sladek signed his cruel Arthur C. Clarke spoof "Carl Truhacker". Hugo Gernsback, SF magazine pioneer, used three subtle pseudonyms in a single issue of his Science Fiction Plus: Greno Gashbock, Kars Gugenchob and Gus N Habergock. Another major editor, the eccentric John W Campbell, appears in Barbarians of Mars as Blemplac the Mad. James Lovegrove's alternate-world novel Provender Gleed features Anagrammatic Detectives, juggling people's names to learn their secrets: "Honestly? Or on the Sly? We can tell you which!"
More devious still are acrostics. One volume of James Branch Cabell's "Life of Manuel" fantasy sequence includes a high-flown sonnet whose lines' first letters spell THIS IS NONSENSE. Vladimir Nabokov's "The Vane Sisters" becomes a ghost story only if you notice that, unknown to the narrator, those two dead sisters have left their acrostic mark on his closing paragraph. Ramsey Campbell's "The Words that Count" plays a similar trick to encode a satanic message. A favourite example comes from the Man from U.N.C.L.E. novelizations published long ago by A.A. Wyn of Ace Books. Unhappy with the miserable pay, David McDaniel caused the first letters of chapters in his U.N.C.L.E. spinoff The Monster Wheel Affair to spell out A A WYN IS A TIGHTWAD.
Finally: Max Beerbohm, author of Zuleika Dobson and other literary fantasies, hatched a 1940 plot to drive Britons insane via the Times crossword. His puzzle had six laughably easy answers to hook the reader; all other clues were meaningless, impossible. The Times printed it ... but nervously published Beerbohm's devilish explanation next to the grid. Thus England was saved from total wartime demoralization, and we won after all.
"David Langford" was once an answer in the Telegraph general knowledge crossword.
Later: a November 2010 Independent cryptic crossword (which I completed but failed to keep) demonstrated that Ursula Le Guin's name has entered the English language. A clue whose answer had to be a kind of weapon featured the phrase "SF author": solvers were expected to think of LE GUIN, which (minus the I) formed part of NEEDLE GUN.