Fun fact: slap was a client command that just sent "action" over the channel/privmsg, which would get rendered as something like: * <nick> <action text> More

Fun fact: slap was a client command that just sent "action" over the channel/privmsg, which would get rendered as something like: * <nick> <action text> More generally, on most clients you could use "/me <text" command to do the same thing. And on the protocol level, it was done by a mini-protocol on top of IRC, called DCC (direct client-connection), that would look like: PRIVMSG #channel :^AACTION text^A (where "PRIVMSG #channel :text" was a way to send a normal message, and ^A is Ctrl-A). DCC was also used as signalling for file transfer. Clients wishing to send files would open a high-end port on their machine and send a DCC message with the file name, IP and port to connect to (similar to active FTP). (yes, I spent an inordinate amount on time on IRC...)