Why can't I take the player sprites from 1 file and take them to another Cave Story?

I tried taking my edited sprites from my broken Cave Story (bigger sprites would fall through the ground) to a new file, but after I overwrote the new MyChar.pbm file with the old MyChar.pbm file, when I tried to open the Cave Story game, it kept giving me an error regarding the (you guessed it) MyChar.pbm file. I can't figure out why, since the only difference between the two is that the sprites in the old one are edited. Can someone help? I don't want to have to remake all of the sprites.

 

I didn't know I had more posts than kage!

erghhh, I know I sound like a certain phantom, but read the stickies.
In brief, it's because of a check the game runs to see if there is a bit of text at the end of the image files, to fix it, delete that check. There, I told you what to do. Happy?
=P

 

All right then, thanks.
Now all I need to do is find a hex editor. 8D Yay.