It's what makes us all special snowflakes of lies and bitterness. Except John and Jade, you can pretty much take everything they say at face value. [Unless John's pranking you but whoops not Dave's problem, might as well set some up for Egbert to knock 'em down]

The only thing escaping from anyone's control is Terezi's tongue it probably has a mind of its own and tells her what to do half the time.