do a double take
From Longman Dictionary of Contemporary Englishdo a double takedo a double takeSURPRISEDto look at someone or something again because you are very surprised by what you saw or heard → double takeExamples from the Corpusdo a double take• Colleagues and friends often walked past me in the hallway, then stopped and did a double take.• He had to do a double take, bumping into a filing cabinet.• When he got to Mrs Luegerhe had never known her first name-he did a double take.