mix of brain waves and wave length.
when you and your friend say something at the same time or when you say something out loud that has been on your friends mind alll dayyy.
it even comes with song and dance:
*flash hands to right side* bravelength *flash hands to other side* bravelength *make a fast-ish wave motion with one hand* woo woo woo!
it must be done quick and in a cute voice.
person: waow! for a second i thought that was a man!
friend: omg! i was just thinking that!
person: no way!
both: BRAVELENGTH! BRAVELENGTH! WOO WOO WOO!