Due to negative reception of the character in season 9, Sparky did not appear in season 10 of the Fairly OddParents, and was not given an in-universe explaination for his absence.
In the fanfic, Sparky is no longer part of Timmy's fairy family, and is a villain until the episode "Friend or Fiendish Canine", where he gets reformed. Wanda explained that Sparky trashed Timmy's house and blamed him for the destruction, and then ran away.
In this series, Sparky is voiced by Seth MacFarlane instead of Maddie Taylor. His voice is a bit similar to Peter Griffin from Family Guy.