It's a meme, but most cats really aren't. The "make a cat jump by putting a cucumber behind them when they aren't looking" meme works apparently because the cat was distracted and freaks out that something (possibly something that looks snake-like to them?) got near them without noticing, but not all cats jump, and they definitely just look at you like you're out of your mind if you just throw a cucumber in their face for no reason and expect them to be terrified of it.
