make a monkey out of someone

make a monkey (out) of (someone or oneself)

To do something that makes someone (or oneself) seem stupid or ridiculous. I know Greg is only trying to impress Lisa, but he's making a monkey out of himself by telling so many corny jokes. I'm not going to dance too much at the party because I don't want to make a monkey out of myself in front of my coworkers.
See also: make, monkey, of

make a monkey out of someone

or

make a monkey of someone

OLD-FASHIONED
If someone makes a monkey out of you, or makes a monkey of you, they do something that makes you seem ridiculous or stupid. The teenage footballer made monkeys out of men twice his age with his spectacular goals. If you follow the proper steps, you won't make a monkey of yourself.
See also: make, monkey, of, out, someone