You accidently give a friend a regular hoe when you mean to give her a Cosma-poitian. (This was in return for a nice gift she had just given me. I am sure she was thinking "HUH?" but was too polite to say anything. I only realized it when she was on the next street.)
you're IMing with a friend and you say something particularly embarrassing or stupid and realize you have just accidentally typed it in the Live Help window instead.
You see someone who looks exactly like your friend and you want to screen capture the glitch to show your friend but end up looking like a total creeper cause they keep moving and you have to chase them!
The Smuggler that you have been hoping to meet tries to recruit you and you press the wrong option and he disappears. Fortunately I have been able to assist him twice since then.
... someone types "test" in the chat to make sure it's working, and you attempt to answer "you pass" but you leave off the "p"... in Live Help... and you're a Guide. (honest, it was a typo, I swear!)
You sell your home without picking up all your stuff including your pickle, yeti and dolls. By the time you realize you forgot to pack up someone else buys the home, picks up your pickle, yeti and dolls then deletes their account.
You donate your GNG musicblock by accident. Then yell out loud, bash your head against the keyboard and everyone in the internet cafe stares at you for the next 4 minutes.
you're on your way into Neva Neva and you see someone hanging around outside the door so you ask if he'd like to follow you in, and he replies, "[staff] kevbob: I can get in."
Get the email from tiny speck telling you that your subscription is over and you think that they'll revert you to the noob look if you don't change your vanity features, and then realize afterwards that it was only about the clothes.
you dump four lumps of earth into the bag of the only glitch on the street (whom you are certain is the culprit that dropped it into your bags in the first place), only to read the action history and realize it was in fact the sneaky peat bog that put it there.
Edit: man, now that i look at that...i really do live up to my name. *hangs head in shame*
When you think that you are talking in local chat with the dev about a non-existent door, and, halfway in the conversation, the dev tells you that you have been spamming global. All of whom (in global) wonder why you've stopped the partial-conversation. Even further awk is after you realize that the dev was replying to all of the spam in local, and waiting to tell you about global HALF WAY IN THE CONVERSATION. o.O