The Salmon bot.
Watch for this.

I just got hit with it myself. Fortunately, the guy on the other end was amicable and we were able to determine it was all some sort of mistake, but Jesus, imagine if I had gotten someone less thoughtful.

Low down: if you are on AIM and you update your eljay, this bot will connect you with someone else who has just done the same, beginning with a bogus message. They may also be incendiary: the one I got read "I believe, good sir, that you misspelled 'nigger' in your recent post". Hilarity, I imagine, is intended to ensue for any third party, but it's nothing but a nuisance and potential nightmare for the rest of us.

Some typical iterations (this is not a complete list):
-TyrranicalSalmon
-DevourableSalmon
-ArmoredSalmon
-NoxiousSalmon
-TroubledSalmon
-ReanimatedSalmon
-NumerousSalmon
-ChivalrousSalmon
-SadisticSalmon
-CredulousSalmon
-GhastlySalmon
-NauseousSalmon
-SassySalmon
-PotentialSalmon
-BanalSalmon
-IntriguingSalmon
-DullardSalmon
-EfficientSalmon
-ClimacticSalmon
-HumaneSalmon
-ProtestingSalmon
-PompousSalmon
-DefacedSalmon
-NoteworthySalmon
-ConcealedSalmon
-PropheticSalmon
-SpurnedSalmon
-ZombifiedSalmon
-BetrayedSalmon
-AppliedSalmon
-CredibleSalmon
-WishfulSalmon
-WitheredSalmon
-MorbidSalmon
-ReflexiveSalmon
-RickAstleySalmon <--- ENVY!!
-RalliedSalmon
-TopologySalmon
-BarackSalmon

Just when I was feeling proud of the internet, it pulls stupid shit like this.

Also: themissinghat is a community for victims of this and other nasty bots. The earliest instance I've dredged up for the Salmonbot is this post, recorded on the 9th of this month. There are maybe a dozen or more other iterations logged in this group than what I've recorded here.

IF YOU ARE HIT WITH THIS BOT: The person on the other end has a username you cannot see, and they cannot see your real SN. To allay hostilities or confusion, IM them back politely, explain the bot, and point them to information pages like this one.

Update: It was all a social experiment! Yeah, this doesn't have "4chan asshole" written all over it....