It was rumoured that while filming the gas mask scene, David Tennant forgot his line, and he spontaneously ad-libbed "Are you my mummy?", the catchphrase of the gas mask zombies in the Christopher Eccleston serial The Empty Child (2005)/The Doctor Dances (2005). However, his wife Georgia Tennant confirmed that this isn't true.
Donna was originally meant to use a shoe to knock out the Sontarans but because Catherine Tate only wears trainers they didn't want it to be a trainer, or they thought a trainer would be too soft and just bounce off the back of the neck. She got to use a mallet instead.
When preparing for the nuclear strike, all countries with known nuclear capabilities check in, except for Russia. The very last to check in is North Korea, of which it is disputed they have nuclear weapons, at which point the Colonel looks very surprised.
Donna Noble's initial pronunciation of the name "Sontaron" is an in-joke mirroring a disagreement in the original production of The Time Warrior: Part One (1973), where director Alan Bromly suggested the "Saunter-on" pronunciation and was overruled by Kevin Lindsay who used his position as portrayer of the Sontaran Linx as authority of knowing how to pronounce the name of his species.
Donna Noble gets a key to the TARDIS, the first of 2 signs that she is the new companion, the other being a cell phone upgrade.