Cheap - cheaper, the cheapest.
Interesting - more interesting, the most interesting.
If "little" means "small in size," the comparative is "littler" or "more little", and the superlative is "littlest". If "little" means "small amount of," the comparative is "less", and the superlative is "least".
Loose - looser, the loosest.
Healthy - healthier, the healthiest.
