Yes, it’s possible, my brother made a level editor for Super Mario 64! It is so addicting to make your own stuff in each level. I made Bob-omb Battlefield into a fire level, the mountain being a volcano. I changed all the goombas into pokeys, (the cactus) and much, much more.
Whoever wants a copy of the level editor (SM64project) can email me (firstname.lastname@example.org) and tell me WHY they want it.