沐猴にして冠す[mokkounishitekansu] to be an incompetent leader (like a monkey wearing a crown)
沐猴[mokkou] monkey

猿猴[enkou] monkey (esp. a gibbon)

意馬心猿[ibashinen] (being unable to control) one's worldly desires and passions
猿轡をかます[sarugutsuwawokamasu] to gag someone
猿も木から落ちる[sarumokikaraochiru] even monkeys fall from trees
猿回し[sarumawashi] showman who trains performing monkeys
猿ぐつわ[sarugutsuwa] (mouth) gag

猿股[sarumata] undershorts
猿芝居[sarushibai] monkey show
猿まね[sarumane] indiscriminate imitation (lit: monkey imitator)
猿人[enjin] ape man