An urban legend states that Arnold was mistakenly cooked and eaten by the Green Acres cast. In actuality there were several Arnolds that often ranged in age, size, color and even sex, which is why Arnold inexplicably has grey hair, spots, and even teats in some episodes.
Also, the avg. pig life span is 12-20 years, so obviously no pig from the series could have appeared in the TV movie over twenty years later.
Also appeared in the made-for-TV-movie, in 1990, entitled "Return to Green Acres," reprising his role as Arnold Ziffel.