How do you make your Sim know everyone?

You can do that by opening the cheat code window (ctrl+alt+c) and type in Boolprop TestingCheatsEnabled true. Hold shift and click on the mailbox. There it should be an alternative to "let me know everyone" or something. If you want to be friends with many of them, you can simply choose "make friends for me" (or something similar) and then you become popular!

P.s. You become very popular, and your phone keeps ringing all day.

p.s THIS DOES NOT WORK I TRIED IT