Assuming by 'Mario sprites' you mean the main player character:
- Extract GFX using Lunar Magic
-
Download YY-CHR
GFX32.bin is Mario's main file. There are little pieces of hands and feet used for running and swimming and cape in GFX00.bin. Depending on your needs and how you draw your character, you might just be able to delete all the floating hands and feet in GFX00.bin.
Get
Player Tilemap Editor if you aren't drawing the poses in the exact same place (e.g. big standing frame on top of big standing frame)
You have two options here:
1) Adjust the palettes and draw the new character manually (Recommended you import the palette from Lunar Magic and adjust the bars of palette 8)
2) Rip from a sprite sheet. I could not find a sprite sheet of Crash Bandicoot on spriters-resource.com and I assume from your post history and profile that this is what you'd be after.
When you make the character palette, try to change the last half of palette 8 first because the last three quarters of the palette change with powerups, and the first 8 colors are used by tons of other sprites. I'm sure you could fit Crash's oranges and blues in, including enough for shading.
Google some concept art - your avatar is a good example, but have more pictures since there are 3 main angles you're going to be drawing him (side or profile, front, and back.) If you lack drawing skill,
here's an excellent guideline. Pixel art is very different from art on a physical canvas because you can point and click and change anything, and with enough time, form it to anything you want.
In short, changing Mario isn't quick and probably never will be. It's easy if you have the motivation though. I just hope you like drawing.