do a double take
To look twice due to surprise or disbelief. Everyone did a double take at his shiny new sports car as he drove by. Men and women alike did a double take when they saw him in his tuxedo.
double take, do a
Show a delayed reaction to an unusual remark or circumstance; also, look at something or someone again. For example, He did a double take when his ex-wife appeared at his wedding. [1930s]