This extension acts as an aide for StackExchange Chat users and provides different local commands to help you!
Chat Commander is a client side Chrome extension that integrates commands for your use on any Stackexchange Chat.
So far there are these commands here
/replyLast <username> <message>
/cat <type if you want, jpg, png, or gif>
So, collapse and uncollapse are self-explanatory, they take any onebox chat message (Wikipedia, SO Question/Answer, Youtube, Image, etc.) and collapse it
/giphy will send a Gifs to the chat according to anything you send after it.
/shruggie will send a ¯\(ツ)/¯
/replyLast will reply to the last message sent with the message .
/cat will post a random cat picture