Join the club

A way to show agreement, but also to tell someone they aren't the only one. Often used when the person saying it is responding to someone who obviously hasn't experienced as much on the topic. Can be similar to "welcome to my world."

Person 1 (barely knows Katy): "Wow I can't believe how annoying Katy is"

Person 2 (known Katy for years): "um YEAH, join the club, now you know why no one wants to be around her."