You can make the UFO appear on the menu screen. It's not difficult! Just move the cursor over the menu buttons 3 times, but follow this order:
1. Adventure
2. Gauntlet
3. Options
4. More Games
5. Quit
Also you can stop the stars on the space level. This will help you to focus on the screen. So, when you are on the last stage 13-1, press "s" ans thus you will make annoying stars stop.
Want to make frog eyes follow the cursor? Then use this cheat! While in the menu, make a click on the frog which is sitting in the lower left corner of the screen. Since then, this creature will be watching your cursor. Click on it again to make the frog stop watching your cursor.