The idea here is to take a transcript of an old conversation from iChat and alter it after the fact to make it appear that people actually said different things. Tricky!
Without further ado:
First off, make sure that iChat is set to keep transcripts of chats:
Open iChat preferences:
Go to the "Messages" tab, and check the box that says "Save chat transcripts to:" (if you're feeling wild and crazy, you can even select where the transcripts will be saved).
Now have a conversation:
Finish the conversation, and close it.
This is where the fun part begins!
First off, get hold of a hex editor. I use HexEdit, but a quick google search will find you something compatible with whatever platform you are using.
Now, open the transcript of your conversation in HexEdit:
It will look something like this:
You can slog through the whole mess if you would like, squinting at it, until you find the section of text that you would like to modify, or you can do a search:
And ta-da, here is the section:
There are two copies of the text in the hex code - modifying the first will change the actual appearance of the chat when you open it again: this is the one that actually makes a difference. Modifying the second one makes it that much harder to tell that the transcript has been altered, so the choice is yours.
In order for this to work, you cannot exceed the original length - if the original statement was 3 characters long, the new text must also be 3 characters. You can make it shorter by adding trailing or leading spaces which were ignored by ichat the first time I tried this back in May, but with later versions of iChat appear to still show up.
Now alter the text:
Save your work, and open the file in ichat:
Success! It now looks like we were discussing world domination. Everyone will be fooled.