Of "The Beverly Hillbillies"were there?And a question:Did they have 2 Christmas crossover with "Petticoat Junction"(and I presume if they did-it was done AFTER Bea Benaderet died)?

I know they had at least 3-one in the first season, where they go back home (and take there first airplane trip) to surprise Pearl and Jetherine, one in the second season where Mr. Drysdale gives them expensive presents hoping they'll stay in Beverly Hills, and a color one (I don't know what season) where they take jobs in a department store, but I don't know if there's any others. (the first 2 are on DVD)

And there was a Thanksgiving episode that was a crossover with the casts of "THE BEVERLY HILLBILLIES", "PETTICOAT JUNCTION", and "GREEN ACRES". And you're right -it was in the post Bea Benederet years of "PJ". I don't think there was ever a crossover one for Christmas, though.

I know they had at least 3-one in the first season, where they go back home (and take there first airplane trip) to surprise Pearl and Jetherine, one in the second season where Mr. Drysdale gives them expensive presents hoping they'll stay in Beverly Hills, and a color one (I don't know what season) where they take jobs in a department store, but I don't know if there's any others. (the first 2 are on DVD)

And there was a Thanksgiving episode that was a crossover with the casts of "THE BEVERLY HILLBILLIES", "PETTICOAT JUNCTION", and "GREEN ACRES". And you're right -it was in the post Bea Benederet years of "PJ". I don't think there was ever a crossover one for Christmas, though.
There was a crossover Christmas episode. It aired in December 1968 and was called "Christmas in Hooterville". This was also a post Bea episode.

^it's also the only color Christmas episode of Petticoat Junction and it also reuses black and white footage from the season 1 Christmas episode (it's also basically the same plot!)