From Longman Dictionary of Contemporary Englishmock surprise/horror/indignation etcmock surprise/horror/indignation etcPRETENDsurprise etc that you pretend to feel, especially as a joke She threw her hands up in mock horror. → mock
Examples from the Corpus
mock surprise/horror/indignation etc• No wrong questions, no mock surprise.• She threw up her hands in mock horror as the little pomeranian ran yapping among the guests.• With mock surprise, he settled into the love seat, draping his arms along its top. 