When you invite someone to a small get-together and they show up with a large group of people (their crew) you don't know, often greeting you with "Is it okay that that they came?" What are you gonna say???
A treasonous uninvitation.
A take on "Et tu Brute?" - Caesar, before Brutus stabbed him
"Hey Matt, who are all these people?"
"Oh, sorry man. Is it cool if they come too?"
"Et Cru Matt?"