Metal Slug: 1st and 2nd Mission are the very first portable Metal Slug games for the Neo Geo Pocket, developed by the original employees of SNK before the company went bankrupt in 2001.

From what I gathered, there's 2 ways to effectively rip the sprites: use YY-CHR on the roms of these 2 games, or just screenshot the sprites appearing on-screen by pause-and-play via the NeoPop or BizHawk emulators.

Using this program on the roms of MS: 1st and 2nd Mission is a bit similar to using it on a .gba rom of Metal Slug Advance, in the sense that you'll have to play a bit with the + and - buttons to correctly display the tiles. You'll also have to use a 8x8 checkered background to help you out during the "piecing tiles back" part.

There's apparently a problem with this program, where the language may be distorted after installation. In this case, download the C# version.


When you open either of the 2 roms with YY, be sure to change the BPP from "2BPP NES" to "2BPP NGP".



Now let's take the Zeppelin from 1st Mission as an example:



At first, the tiles are mostly unrecognizable. Shocker there!
You need to play with the '+' and '-' buttons until the tiles are correctly displayed.



There you go! Now the tiles just need to be pieced back from left to right.
For the palettes, you can use a screenshot of the games in action and apply the screencapped palettes to the tiles.