Early Steve on the left.
General:
- Originally, Laura Prepon (Donna from That '70s Show) was supposed to voice Hayley Smith, but was replaced by Seth MacFarlane's sister, Rachael. Had Prepon stayed, the show would have gotten a lot more unfavorable comparisons to Family Guy as the latter show also has someone from That '70s Show as a cast member (Mila Kunis replaced an uncredited Lacey Chabert on Family Guy and played Jackie on That '70s Show).
- According to the commentaries, the original plan for Roger would've been that season 1 would've had him be stuck in the house all the time, but get fed up with it in season 2 and try the disguises. They would've worked until season 3, where Roger gets revealed in public and it becomes a giant media scandal. But by season 4, everyone would've gotten used to aliens and stopped caring, making Roger try to become the hot new story with schemes.
- Klaus was originally supposed to be a Frenchman, but Dee Bradley Baker didn't know French well, so they retooled the character to make him German, since Baker can do a German accent and spent enough time in Germany to know some words.
- John DiMaggio, Rob Paulsen and Billy West were considered to voice Klaus.
- Steve also had a different design (read: he was really skinny and awkward-looking), and was going to be voiced by Family Guy writer Ricky Blitt. This design can be seen on an early trailer for the show on the Family Guy: Freakin' Sweet Collection DVD and the unaired test pilot that was leaked online.
Season 1:
- The Golden Turd storyline was originally to be ongoing within the first season instead of being spread out over multiple seasons (and often years). The second installment was originally to happen in "Stannie Get Your Gun" and made it as far as being fully animated before being cut for time (but can still be seen however in the deleted scenes of the Volume 2 DVD set), while the third installment would've happened in "Rough Trade". The actual second installment in the following season's "Failure is Not a Factory-Installed Option" essentially combines both of the stories of the original planned installments into one.
Season 2:
- The idea of Toshi marrying Svetlana at the end of "Of Ice and Men" was initially to be followed up on in a later episode as a subplot with Steve, Snot, and Barry giving him a bachelor party.
- Jane Fonda, Donald Sutherland, and Martin Scorsese were all offered the opportunity to voice themselves in "The Best Christmas Story Never Told" but all three declined.
- A rejected idea for "A.T. The Abusive Terrestrial" was for Roger to go back to the family he was with prior to the Smiths, who would've been played by Henry Thomas and Drew Barrymore (Elliott and Gertie respectively from E.T. the Extra-Terrestrial).
- The original draft for "Four Little Words"note involved several CIA agents being mysteriously killed and Stan believing that Bullock is the one behind it.
- The season finale "Joint Custody" (the episode where Stan and Roger try to bust Jeff on growing and selling marijuana in Florida) was originally conceived as a way of continuing the Golden Turd storyline with the death of Mrs. Marylin Thacker from the previous installment either in a condo pool in Boca Raton by an alligator or being killed by a liquor store delivery man to steal the turd to give to a Cuban crime boss to save his sister. The idea was ultimately cut for time and it would be another eight years before another installment was featured in the Season 10 episode "Blagnarst: A Love Story" (which focused on Marylin's district attorney son finding the Golden Turd and calling an oil company magnate for financial support on his campaign to become Senator).
Season 3:
- Several endings were proposed for "Dope & Faith" due to the crew having a hard time coming up with one. One such ending would've had Stan meeting Brett's brother at his funeral and befriending him when Stan learns that Brett's brother does believe in God.
- Michelle (the Ghost of Christmas Past) from Season 2's "The Best Christmas Story Never Told" was to return for "The Most Adequate Christmas Ever". Her role in the episode was ultimately given to a new character with the same name due to negotiation issues with Lisa Kudrow (the voice of the original Michelle).
Season 4:
- A subplot was originally conceived for "Escape from Pearl Bailey" where Francine buys Roger his very own star. It was completely removed when the writers ended up making the main plot the only story of the episode. The rejected storyline was used in a later episode when Hayley buys a star that turns out to be Roger's home planet.
- One of the families that Roger would have been adopted into on the episode "Family Affair" was The Griffins from Family Guy.
- Seth Rogen was originally set to play Etan Cohen in "Bar Mitzvah Hustle". However, he was considered too mature-sounding, so he was ultimately replaced by Seth Green.
- The first choice for the role of the Delorean door salesman in "Delorean Story-an" was Christopher Lloyd. However, he declined, resulting in Joe Flahertynote getting the part.
Other episodes:
- The initial idea for what would be done with Hayley after she and Jeff conned Stan out of his $50,000 in "100 A.D." is that we would briefly check in on how they were spending the money in the episodes until her return in "There Will Be Bad Blood". Ultimately, this was scrapped to have them spending it all over the course of a single episode in "Son of Stan" in order to get away from Roger.
- The Season 7 episode "Hot Water":
- The "Chuck Berry me over Germany" line from "Hot Tub of Love" had several different variations including "Throat Choke me over Germany". Additionally, the song was originally to be sung by Seth MacFarlane instead of CeeLo Green.
- The episode was originally conceived as the series finale, simply because they had no idea if the show had been renewed or not and figured "What better way to end the show than by killing the main character?". Ultimately, the show was renewed and this episode was written off as being non-canon.
- The penultimate Season 17 finale, "Echoes", was originally produced as a potential series finale, as the Warner Bros/Discovery Inc. merger was happening around the same time, with the crew being unsure if they'd be renewed or not, fortunately, TBS renewed the series for two more seasons before the merger closed.
- They were later proven right to be concerned, as Warner Bros. Discovery tried to cancel the show and asked Disney if they could back out on producing an 18th and 19th season, fortunately it didn't succeed.
