Commander Keen Episode I: Marooned on Mars Cheats
Press and hold T + A + B for 99 rounds of ammunition and an extra life.
Press and hold G + O + D. Activating this code will also let you jump better
Press and hold C + T + SPACE to get the pogo stick, all key cards, and ray gun charges. Or push CTRL + TAB + SPACE.
Push SHIFT + TAB when in the map level.