Betty Rubble was voiced by Bea Benaderet (1960-1964) and Gerry Johnson (1964-1966). Benaderet is also known for playing Gertrude Gearshift, Kate Bradley, and Pearl Bodine. Johnson was better known for theatrical roles in the Dallas Theater Center.
The Mexican Spanish dub deserves an special mention: Fred (and also Barney for a few episodes) in the original TV series was dubbed by Mexican comedian and actor Jorge Arvizu, who also voiced Bugs Bunny and Maxwell Smart and he's maybe the most iconical of all the voice actors who voiced Fred in Mexico. In other animated incarnations, he's voiced by Arturo Mercado (Speed Racer and Simba) who was the second most know voice actor for Fred in Spanish and he also reprised that role in the live-action film. Humberto Velez (Homer Simpson) also voiced Fred in the I Yabba-Dabba Do! direct-to-video film. Barney was voiced by Julio Lucena (who voiced Top Cat), in other animated adaptations and in the film, he's voiced by Francisco Colmenero (who voiced Pumbaa) and in I Yabba-Dabba Do! direct-to-video film, Alfonso Obregon (Kakashi Hatake and Shrek) voice him too.
No Export for You: At least in syndication — an episode in which the Flintstones encounter a group of stereotypical Wild West Indians was successfully banned from broadcast in Saskatchewan after protests from Native American groups. The ban became moot when the show began airing on nationally broadcast cable networks and came out on DVD, however.
Old Shame: The Flintstones cast promoted Winston cigarettes during the show's first two seasons. Amusingly, those ads are now among the only vintage tobacco commercials that one can easily find online (since showing them is technically illegal just about everywhere on the planet).
The Other Darrin: Hanna-Barbera voice actor Daws Butler replaced Mel Blanc as Barney Rubble for a few episodes in 1961 while Blanc was hospitalized after a near-fatal car accident. Hanna-Barbera, however, did not publicly acknowledge this, and Blanc was still listed in the closing credits. There was one episode where it started with Daws Butler as the voice of Barney and right in the middle of the episode, he's replaced with Mel Blanc (and, unlike most modern shows where there would be a fourth wall-breaking joke about it, this mistake slipped by completely unnoticed).
Post-show examples. At this point, all of the original Flintstones actors, except for John Stephenson (the voice of Mr. Slate), have died and been replaced (some multiple times).
Gerry Johnson replaced Bea Benaderet as Betty Rubble in the show's fifth and sixth seasons, when Benaderet left to concentrate on her role as Kate Bradley on Petticoat Junction. Johnson died soon after The Flintstones ended its ABC run and would be replaced in 1971 by Gay Hartwig (Benaderet herself died in 1968, during Petticoat's run). Hartwig herself would be replaced by Betty Jean Ward, who was replaced by current voice Grey DeLisle.
Aside from the aforementioned period of recuperating from his car wreck, Mel Blanc voiced Barney up to his death in 1989. Since then, Barney has been played variously by Frank Welker and Jeff Bergman (and Seth Mac Farlane in parodies shown on Family Guy and Robot Chicken).
Jean Vander Pyl was the longest-surviving female member of the principal cast, playing Wilma until her death in 1999. Since then, Wilma has been played by Tress MacNeille.
The 2nd movie recasts all the characters due to taking place before Fred and Barney were married to Wilma and Betty
Recycled Script: There have been numerous episodes where Fred had a doppelgänger and in a TV movie from the 1970s, Fred took Santa's place. He did the same thing in the original show.
Recycled Soundtrack: In a sense. Mel Blanc's previously-recorded yaps for Dino from the original series were re-used for the films. Blanc himself had been dead for five years by the time the first film was released, and his voice was initially used without a screen credit, prompting his estate to slap the studio with a lawsuit before one was put in for the home video release.
Several Hannah Barbera series from around the same time used the show's stock music, most notably The Yogi Bear Shownote A couple episodes of which even have what would later become "Meet The Flintstones" snuck into the music.
The script for the first episode had Fred saying "yahoo". Alan Reed didn't like it, and asked whether he could change it to "Yabba-dabba-doo".
Barney's Vocal Evolution came about when Mel Blanc suffered brain damage in a car accident. When he came back to work, he suddenly started using that deeper voice for Barney (which was also a much closer imitation of Art Carney's voice - even though Blanc had originally refused to ape Carney) and no one said anything.
At one point, Richard Donner was attached to direct, Joel Silver was going to produce and Jim Belushi was going to play Fred. When the movie went from Warner Bros. to Universal, Donner stayed around but had to pull out due to conflicting schedules with Maverick.
Moranis claims in an interview that John Candy was taking the role of Fred originally, but his death before filming ended up placing Goodman in the role at the last minute, which would mean that the movie was filmed and released over the course of little less than 3 months. Hollywood moves fast, apparently.
The role of Sharon Stone the secretary was written for...Sharon Stone, but due to scheduling conflicts with The Specialist, she dropped out and Halle Berry signed on.
Janine Turner was considered for the role of Betty.
Fred and Wilma were originally to have had a son, Fred, Jr. He was cut from the show's final series' bible, but a Golden Book that was based on the original ideas was released just as the show debuted. Maybe Pebbles' older brother ran off with the original, intelligent Dino?
Jackie Gleason was not happy about learning that Fred Flintstone was based on him without his permission, nor that the Flintstones was based on his old TV series The Honeymooners and tried to file a lawsuit for using his likeness, but friends and colleagues dissuaded him from doing so in light of the show's popularity, telling him it would be bad for his reputation if he became known as "the man who killed Fred Flintstone."
Seth Mac Farlane was originally going to revive the show for FOX, possibly as a replacement for The Simpsons, which was about to be canceled in the middle of season 23 due to money issuesnote the last episode would have been the Christmas Episode in the future where Bart tries to bond with his kids while divorced from Jenda while Lisa tries to bond with her teenaged daughter and Maggie is pregnant. Unfortunately, MacFarlane shelved the show after the cast and crew of The Simpsons took a pay cut to keep the show afloat.