Different kettle of fish 

a completely different type of person or thing from the one previously mentioned.

"the new office is a rather different kettle of fish"

Different kettle of fish by Arminkshipper April 20, 2025

A whole different kettle of fish 

a different situation or person to be dealt with

I've watched you a lot on Instagram, but in person? Whoof! That's a whole different kettle of fish!

A whole different kettle of fish by johnzilla1126 May 19, 2024

a diffrent kettle of fish 

a different situation or person to be dealt with

Breakfast was a very different kettle of fish here in America.

a diffrent kettle of fish by Choonmann Sung September 28, 2006