"The One Hundredth" was co-written by show creators David Crane and Marta Kauffman and directed by Kevin S. Bright. The episode takes place in a hospital, meaning none of the usual filming sets were used, thus surprising several members of the audience. Crane commented that the hundredth episode was a "big milestone" for the series and to mark the major event, Lisa Kudrow's character Phoebe would give birth to triplets. This brought a culmination to the surrogacy story arc, which began in the fourth season; it was developed to accommodate Lisa Kudrow's real life pregnancy. When Kudrow accepted the surrogate mother storyline, the idea of having more than one baby was "comically funny" to Kauffman, and giving birth to triplets or "their brother's children" was something never seen on television. Phoebe's pregnancy gave the writers incredible license for her to "be just outrageously mean and still have it be funny". In order to prepare for the labor and birthing scenes, Kauffman watched a video of her cousin giving birth.