Грамматика - Степени сравнения
Правильно: «greener, funnier, happier, nearer, wickeder / more wicked, cleverer / more clever, commoner / more common, handsomer / more handsome, narrower / more narrow, quieter / more quiet, shallower / more shallow, simpler / more simple, stupider / more stupid, more fun, more quickly, more crowded, more boring, more careful, more often».