Mulder and Scully move into a peaceful neighbourhood together posing as a newly married couple.
There is some sort of creature, maybe a swamp monster, attacking the residents.
Mulder gets the impression it's the neighbours that are behind the attacks so he decides to annoy them as best he can.
At some point Mulder puts up a basketball net in the drive way, he also does some other stuff to annoy them.
Eventually the neighbours summon the swamp monster to kill Mulder and Scully.
This sounds like the episode "Arcadia" (S06E15).
From wikipedia:
Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) investigate the Klines' disappearance, going undercover as new homeowners under the aliases Rob and Laura Petrie. As Mulder and Scully are moving into the Klines' former home, neighbor Win Shroeder nervously tucks away Mulder's basketball hoop into the garage, telling him that it is against the community's CC&Rs.
(snip)
After dark, Mulder brings out his basketball hoop, and Shroeder runs over to frantically argue with Mulder to put it away. Meanwhile, something comes out of the grass at Mrs. Shroeder, who screams. Mulder chases it away, but they all notice their light has burned out.
(snip)
Mulder says the creature is a Tulpa, a Tibetan thoughtform, that Gogolak conjured to assure compliance with the HOA rules.
