This seems far too simple to me, but in my house it would be a matter of "you are not allowed on the couch." If the animal cannot somehow be brought in touch with this rule, then perhaps keeping the animal caged is the answer.
My theory always stands that if I cannot get away with leaving the seat up in the bathroom, then the animals cannot get away with breaking the rules either.
Animals aren't as dumb as people make them out to be. Any more than most women make men out to be. All animals can be trained. ;)