Is it possbile there was 3 different Catwomen Mr Frezze and 2 Riddlers

It's called suspension of disbelief. 

John Astin could have passed nicely as a Riddler replacement, had he dyed his hair light brown and... lol that mustache! Why didn't he just shave it off? Was he trying to pull a Cesar Romero? (at least he didn't cover it with skin-colored makeup) Whenever he was on screen, I saw Gomez Addams! And his performance was way too subdued compared to the energetic, maniacal Frank Gorshin. Still better than Maurice Evans as Puzzler though.

A friend of mine suggested Catwoman could've simply had a beach vacation and returned with a nice tan, but Eartha was shorter than Julie and their faces/body types radically different as well.

As for Freeze... I've got no idea. George Sanders looked like a regular guy. Then they made the jump to the nightmarish Preminger with bald head, bluish complexion, red (!!) eyebrows and heavy german accent. Wallach appeared to be a fusion of the two previous versions. 

It was simply a casting decision. The primary actors weren't available so they hired someone else. Continuity was never a big issue for the shows in the 1960's. (Nor for most of the comic books as well )

Didn't Frank Gorshin return for a later episode?