I posted this on another thread with some other information, but from what i've gathered and seen, this is what i've noticed....

Pumpkin Blob Locations
Dojo (Rare)
The Joint (Common)
Swamp Entrance (Common)
Mod Fountain (Either or)
Sardon's Tower (Rare)
Nexus (Rare)
Police Station (Common)
Grotto (Rare)
Place above Sardon's (Rare)