It was the episode where the Rubbles first get Hoppy, with the families going on a picnic to a park (and a picnic basket getting stolen in secret by Yogi, dressed in normal and not "prehistoric" garb). -B.
Sorry, that's incorrect. Yogi and Boo-Boo cameo'd in
Swedish Visitors, the Season 3 finale famous for "He is Olle, you are Sven". It was just the three Flintstones camping out without the Rubbles. You're referring to
Hop Happy, the Season 5 premiere and the first episode in which Gerry Johnson voices Betty.
Yogi and Boo-Boo also cameo in the Snagglepuss episode
Remember the Daze. Fitting, as it takes place in a TV studio.
Yogi turning up at the end of the Augie Doggie episode
Pop's Nature Pup.
There weren't too many other H-B cameos outside of the various Yogi & Company reunion shows- especially TREASURE HUNT, which featured walk-ons by Hokey Wolf, Mr. Jinks, Squiddley Diddley, Ricochet Rabbit, Maw Rugg, Baba Looey, Col. Fuzzby, Granny Sweet, Magilla Gorilla, Penelope Pitstop and probably others. All I can think of is:
-The oft-mentioned "3,000,000th rerun of the FLINTSTONES" as viewed by Elroy Jetson's delinquent classmate. BTW, contrary to popular belief the footage of Fred diving on top of Barney as seen on Kenny's wrist-o-vision is
not from an old episode, but entirely 'new' footage. For years I slavishly scanned every FLINTSTONE rerun for it, to no avail.
-Mumbly turning up at the end of the first
Dynomutt episode. Interesting in that both characters bowed on Saturday AM the same day.
-LAFF-A-LYMPICS, largely a 'reunion show', did feature a silent cameo by Peter Potamus, and several appearances from Jabberjaw, Fred and Barney- the latter two as guest commentators.
There were many more verbal references to other characters in H-B series. Virtually every 1959-62 character, after taking a blow to the head, would say "Like Quick Draw McGraw says,
ooohh, that smarts!" If a character was turning on a TV, it was to watch another H-B show.
Outside of H-B, a
Super Chicken segment involving the Easter Bunny opened with a head shot of virtually every previous Jay Ward character under Paul Frees narrating "There have been many beloved characters-"
A real oddity was the BEATLES episode
Tell Me What You See featuring Ringo momentarily turning (due to a special-effects machine) into fellow KFS property Swee'-Pea.