Hi, folks. I found a couple of cheats in both versions of Dorabian.
Doraemon Dorabian CD: At the title screen, when it says "Push Run", press: I, II, I, II, Up, Up, Down, Down, II, I, Select... to see the ending cinema.
Doraemon Dorabian HuCard: as above, press: Up, I, II, Down, II, I, Right, Left, II, I... for a level select!
If you make a mistake inputting these, you'll have to reset to try again.
I just finished the HuCard version, and the last boss is probably the biggest sprite* I've ever seen on the PCE!
*group of sprites, of course.