"You could have fooled me" is a phrase commonly used to express disbelief or skepticism towards a statement or situation. However, there are several other words and phrases that can be used in its place. Some examples include "I'm not buying it," "That's hard to believe," "I have my doubts," or "I'm not convinced." These phrases convey a similar message of doubt or disbelief, but may offer a slightly different tone or level of skepticism. It's always important to choose the right words to accurately express your thoughts and convey your message to others.