When you start a new game in the registered CD version, you can get to the
hidden planet by entering "Terminal" as your name and "Reality" as your
call sign.  (Both of these are case sensitive.)  Before you start playing
the hidden planet, a message appears saying you are flying the TV-302, a
new, experimental ship.  As far as gameplay is concerned, no, you're not
flying a new ship; this is simply an element of the game's storyline.
The hidden planet is not in the shareware version or the disk based
registered version.

Also, in level 3-1 of Terminal Velocity, fly close to the ground near the
coordinates (63,227).  You will see a photographic image of the Terminal
Reality team.  If you fly too high, the fog will obstruct the view.  A
clearer version of this can be found as a GIF file on the Terminal
Velocity CD in the PREVIEW directory.