Funny Father Amuses Daughter by Dressing Up as a Gorilla

Dressed up as a gorilla, the father amused his little daughter a lot.

'Dressed up' is the correct form to use in this sentence. 'Dressed up' is the past participle form of the verb 'dress up,' which means to put on special clothes or a costume. 'Dressing up' is the present participle form of the verb, used to describe the ongoing or continuous action of putting on special clothes or a costume. In this context, 'dressed up' is the appropriate form to indicate that the father already put on the gorilla costume and amused his daughter.