Since Zelenka's first appearance, David Nykl's fluent Czech was worked into "Stargate Atlantis" as part of Zelenka. Approximately half of Zelenka's Czech lines were scripted (in English), which Nykl then translated verbatim. The other half was ad-libbed and usually included swearing. His usual Czech exclamations include Ty vole and Do prdele. Nykl normally speaks with a Canadian accent, but Zelenka had a thick Czech accent; Nykl found it increasingly hard to remember to put on the accent as the show went on. The late season 1 episode "Letters from Pegasus" features a minute-long non-subtitled monologue in which Zelenka describes the city of Atlantis in his mothertongue. Nykl translated the scripted monologue at home and performed it in Czech the next day. A version in English was initially planned to be filmed but was dropped after Nykl's successful first take. The end of Zelenka's video message ("drž se miláčku" - "take care, darling") was ad-libbed, but Nykl left it to the writers to create Zelenka's backstory. But during the show's run, Zelenka only ever mentions having a brother, a sister, and a nephew, and is never shown to be or have been in a romantic relationship.