Simon Pegg was originally cast as Pete Tyler. Because of scheduling conflicts, he chose the role of The Editor in The Long Game (2005).
Russell T. Davies and Paul Cornell debated whether it should have been Rose's plan all along to save her father; this is left ambiguous in the episode. Billie Piper felt that it did not occur to Rose until after she began travelling.
Bad Wolf reference: The words Bad Wolf are seen on a poster the first time Rose and The Doctor wait for Pete Tyler.