At my organization, no matter how carefully you might curate and select a list of attendees, one or more of them will decide to forward the electronic invitation to one or more other people, just "FYI".  Those people then deem it important for them to be part of the discussion and decision and attend the meeting.  The next thing you know, a 6 person meeting becomes a dozen or more.

Despite telling people not to do this many time, the practice continues.

Am I the only one to experience this phenomenon?

(Sorry, no zombies... :-))