Sparky is the name of a synthezoid dog created by Vision in the Marvel comics. The character was introduced in the acclaimed comic book series, The Vision, which followed Vision as he attempted to create a "normal" life for himself and his family in the suburbs. The story was a big inspiration for WandaVision, and much like the Disney+ series, it saw Vision's attempt at building an ordinary life with a family gradually threatened by matters of death and darkness.
There's darkness in Sparky's story, too. In the comics, the dog was made by Vision after his neighbor's dog, also named Sparky, died in their backyard. But while Vision created the dog in an attempt to keep his family together, the story saw Sparky suddenly beaten to death in a fit of rage by Vision's wife. He was, however, eventually brought back to life by Scarlet Witch and Tony Stark.
Over the course of WandaVision's fifth installment, Sparky is not only adopted by Wanda and her family but also dies from (supposedly) eating leaves from Agnes' azalea bushes. The show hints, through the pleading of her sons, that Wanda may attempt — as she did in the comics — to bring Sparky back from the dead in a future episode. But it's also possible that Vision may just create a synthezoid replacement of the dog.
Either way, Sparky's inclusion in the show may just be yet another sign of dark, tragic things still to come for WandaVision's titular couple.
