Well, I was wrong - Clint Howard was not on Land of the Lost. Someone named Philip Paley played "Cha-Ka", and here's the mini-bio from imdb.com:

"His character Cha-Ka for the 70's TV series, Land of the Lost has become a cult icon. Many poeple do not know (or care) what Philip looks like without his Pacunni outfit -- but that's what adds to much of his mystigue and charm. There have been many women over the years claiming to date him and know him in his post Cha-Ka hay-day, but none of them can produce any proof. Just what does Philip Paley look like? Many wonder, but let's be honest -- do we really want to ruin the mystery."

Now, you know I have to try to find out what this person looked like, don't you?