Completely Different Title: Many countries didn't go with the puny title (though Greece expanded with "Boots, spurs and saddles hot"). Latin America was "Madness in the West", Brazil and Portugal had "A Mess in the West", France was "The Sheriff is in Prison", Germany "The Wild Wild West" (in contrast to that show being "The Crazy Wild West"), Finland "Wild Wilder West", Italy "High Noon and a Half of Fire", Turkey "Silver Saddles", and Sweden followed the "Springtime for Hitler" title for The Producers with "Springtime for the Sheriff".
Frankie Laine's earnest rendition of the opening theme sang came about in part because Mel Brooks never told him the movie was a comedy. Brooks decided to keep Laine in the dark about the true nature of the film, thinking his performance would be better if Laine thought it was an authentic Western.
After he heard it, Brooks didn't have the heart to tell Laine the truth. Laine only found out at the premiere.
Executive Meddling: They tried, but since Mel's contract said that he had the final cut on the film, he sat through the meeting, taking careful notes of all the changes that they wanted to make, and then when the meeting was over he tossed his notes in the garbage.
Mel Brooks as a Native American chief. This is a reference to the early Hollywood practice of casting "dirty whites" such as Jews and Italians as Native Americans. The role's overt Jewishness also goes along with the theme of kinship between marginalized groups in American history.
Jewish-American Madelein Kahn as the very Germanic Lili von Shtupp.
Fan Nickname: The clergyman of Rock Ridge doesn't have an official name, but since he's a clergyman, and since everybody in Rock Ridge is named Johnson, fans often call him Reverend Johnson.
Life Imitates Art: It's unlikely if Mel Brooks knew the story, but in Real Life, a black man was named as the postmaster of Punta Gorda, Florida by a man who held a grudge against the town's founders, as a deliberate affront to its Southern sensibilities.
Mean Character, Nice Actor: Burton Gilliam (Lyle) was quite reluctant to drop all the N-bombs in the script, until Cleavon Little (Bart) assured Gilliam that he would not be offended.
Brooks wanted John Wayne for the role of Jim, the Waco Kid. Wayne rejected his offer because the script clashed with his family-friendly screen persona, but he also found it to be hilarious and told Brooks he'd be "first in line" to see the movie.
Had Richard Pryor (who contributed to the script) been a more reliable actor and/or not coked out of his mind (Mel Brooks found out the truth of the warnings he'd been given when Pryor called on a day he was supposed to be writing to explain he was actually with a couple of girls in New Jersey), he would have played Bart himself, launching his frequent film partnership with Gene Wilder a couple years before Silver Streak.
Wilder himself was a last-minute replacement for Gig Young, who turned up on the set too inebriated to act. Several other actors were considered before Young.