I can now confirm that the 'Electric Jester' achievement should be obtainable as expected. Apologies for the delay in getting this fix out.
In existing save files, you will need to recomplete Spark's mission in order to trigger the achievement but can do so in a save file in which that pygmy is already collected without issue.
As always, reach out to me via email or social media if you find any other issues pertaining to this achievement or the rest of Hop 'n' Marty.
Thanks for playing.