For Pokemon shuffle:
Pokemon in Pokemon shuffle have not been seen as shiny - in any of the 150 main stages, or expert stages. But, nintendo may release a shiny Pokemon sometime in the future. The only Pokemon that is questioned to be shiny is vulpix, but it somehow completely normal.
For Pokemon rumble world:
In this game, it is possible to get shiny Pokemon. Other people have somehow gotten a shiny rattata and shiny bidoof using codes. All the other Pokemon (through balloon stages) have the same probability as normal Pokemon - 1/8192. You should find a few if you continuously play.
Source: Own experiences + opinions and other experiences online
Hope I helped! :)
