Journey to the West / fire mountain
Wikipedia is right.

Sun Wukong disguises himself as Bull Demon King to deceive Princess
Iron Fan and takes away her Banana Leaf Fan. The real Bull Demon King
visits Princess Iron Fan, who then realises she has been tricked. Bull
Demon King disguises himself as Zhu Bajie to trick Sun Wukong and
retrieves the fan.

From the novel:

好大圣，即现本象，将金睛兽解了缰绳，扑一把跨上雕鞍，径直骑出水底。到于潭外，将身变作牛王模样，打着兽，纵着云，不多时，已至翠云山芭蕉洞口，叫声：“开门！”那洞门里有两个女童，闻得声音开了门，看见是牛魔王嘴脸，即入报：“奶奶，爷爷来家了。”那罗刹听言，忙整云鬟，急移莲步，出门迎接。这大圣下雕鞍，牵进金睛兽；弄大胆，诓骗女佳人。罗刹女肉眼，认他不出，即携手而入。
The splendid Great Sage then reverted to his original form, untied the
golden-eyed beast, leapt into the carved saddle, and rode straight up
from the bottom of the water. Once out of the pool he made himself
look like the Bull Demon King. Whipping on the beast he set his cloud
moving and was soon at the mouth of the Plantain Cave in Mount
Turquoise Cloud.
“Open up!” he shouted, and at the sound of his voice the two servant
girls inside the gates opened them for him.
Taking him for the Bull Demon King they went in to report, “Madam, His
Majesty's come home.” At the news Raksasi quickly neatened her hair
and hurried out on her little lotus feet to meet him. Climbing out of
the saddle the Great Sage led the golden-eyed beast inside. He was
bold enough to try to deceive the beauty, whose mortal eyes failed to
see who he really was as she led him inside, hand in hand.