Mama's appearance was inspired by a painting by Amedeo Modigliani, owned by Andy Muschietti. The same visual was used again a few years later, as the painting come to life that terrorized young Stan in Muschietti's It: Chapter One (2017).
It would take four hours every day to get Javier Botet into his Mama make-up, and another two hours to remove it.
This is not the first time Javier Botet has played a ghoulish woman, as he previously appeared as the possessed patient zero in [REC] (2007).
The screenplay is written by siblings Andy Muschietti and Barbara Muschietti, expanded from their previous short film of the same name.
The curator of the archives describes a ghost as "an emotion bent out of shape, barely human, condemned to repeat itself". This is, almost word for word, how the main characters define ghosts in 'The Devil's Backbone' (2001) and 'Crimson Peak' (2015). Both movies were directed by Guillermo del Toro, the later also starring Jessica Chastain. Del Toro provided much of the financing of this film, having read the story by director Andy Muschietti and quite keen on supporting upcoming talents.