http://www.morphos-files.net/find.php?find=lemmings

its not lemmings but its funny and has the same gameplay.

If your program crashes then its not written for Morphos maybe there is already a ppc port of it?
There has been a list of 68k programs that have been tested on ppc as far as I remember:
http://morphos.lukysoft.cz/

have fun