The phrase we've known each other circulates online as a standalone reaction clip, shared on soundboards and reused in short form edits where a familiar relationship needs to be stated quickly. Because the wording is plain and instantly understood, creators apply it to best friends, long term partners, gaming duos and even pets they treat like family. Its popularity comes from that flexibility, letting a serious line work as both a sincere tribute and a joke about people who have only just met.