Uh, the messages from Prepper don't have "BOO!" tacked onto the end. I also see you were messing with Talk using that.
It happens..
If you have something enteret in console and some command or console error smaller than your entered command, it adds that to the end for some reason...
EX:
You entered: TALK("BOO!");
A CONSOLE COMMAND: I see you!
What you see: I see youBOO!");