The Backyard Lab is an Heirloom stage in King of Cards. It can be unlocked after going through the House of Joustus. Here, Hedge Pupil sells the Rat Bombardier Heirloom, a secret device created under the specific request of King Knight, and is also recruited in this stage after traversing it.
This stage is the Hedge Family's house, first seen in Plague of Shadows while visiting the Village, albeit at an increased scale compared to that appearance, plus a stretch of wilderness behind it, which includes a cave.
As the house has a secret tunnel underneath it that leads towards the true hidden entrance of the Potionarium, in Plague of Shadows, Plague Knight decided to blow up the house to gain access to it, as he was unwilling to wait two whole weeks for the locksmith to come and find a replacement for the lost key of the front door, much to the chagrin of Hedge Pupil. By the end of the campaign, the house can be seen having been fixed.
The building, still in his scaled-down appearance, could also briefly seen during the credits of Specter of Torment, where Specter Knight leaves an injured Reize in the care of the hedgehog brothers.
Hedge Pupil can be seen losing the keys of the house in the ending of King of Cards while blowing up the Cavern of Joustus, which down the line would lead to the destruction of the house.
In the Puzzler Pack DLC, the Hedge Farmer can be seen having recreated inside the Pocket Dungeon a small burrow for himself at the Hedge Farm, in an attempt to copy his family's home; said burrow, accessible thanks to Mole Knight's dig ability, even contains a family portrait.