To unintentionally "Reply to All" to an email pertaining to a sensitive and/or volatile subject matter with a direct, crass or sarcastic remark intended for everyone but the original sender. The “Reply to All” message is typically formatted in a manner that will embarrass, enrage or baffle the original sender.
Alternatively, the “Reply to All” message can often be an inside joke to all recipients except the original sender leaving the original sender feeling like a douche (see also douche hat, douche face, douche nozel, douche hydrant or, on a completely unrelated topic, see hot pocket because it’s hilarious).
Al - Hey, remember that email I sent you, John, Ted and Bill the other day about how I was going to tea bag Walt’s wife on Walt’s desk because of Walt’s stupid self-righteous email about the TPS Report cover sheets? Well, I totally pulled a Shelly and hit ‘Reply to All’.
Walt – Whoops.
Al – Yeah, whoops. Whatever. I’m still going to drop a hot pocket in that convertible sofa in his office.
The smelly shelly test is to sniff fingers for aroma of genitalia. Let me sniff you for smelly shelly. I love to sniff my smelly shelly. Why everybody sniffing me smelly shelly. Rosie meet smelly shelly! If you don't believe me sniff my smelly shelly. Mr. President may we toke on smelly shelly cigars?