The Lab Ending is one of the four endings and the current three achievable endings in Pet Story.
The player must choose to go into the vents instead of the entrance, however, they still need to find a way to get to the vents as it is a high distance from the ground. The pets then need to go around the front of the shelter in order to find objects that they can stack up on. Once so, they are able to go into the vents to view an Animal Control Guard talking to a doctor. The guard then says that the pets didn't use the entrance much to the doctor's frustration and resorts to Plan B by first activating the air conditioner in the vents then sending in the Roborats later. The player then spies Slicer in the incinerator room from a vent above. The doctor then says that Slicer failed to lure the pets into his location and then takes him for his next experiment. Curious of where Slicer has gone to, the players then decide to follow the doctor to view where he has gone. This leads to a secret laboratory being discovered. Unfortunately, the doctor notices the pets and suck them out of the vents. The doctor then introduces himself as Dr. Flea and has a plan to rule the world by turning normal pets into Robopets. An example given upon this is that he revealed to turn Slicer into a Robopet called Roboslicer. Dr. Flea then leaves the laboratory to have Slicer battle the player. After Slicer is defeated and Canela is rescued, the player then rushes Slicer to the Adoption Center.
At the Adoption Center, Susie is shown to heal Slicer, as the dog thanks the player for saving him from Dr. Flea, although the mad doctor still has more tricks up his sleeves. Shortly after, Susie reveals to Slicer that he has a surprise. From there, Doug enters the room to adopt Slicer.
See the Classic Ending for if the players use the Entrance. Also, see the Sewer Ending if the players decide to ignore Pigeon or the Zoo Ending and Aquarium Ending for if the players decide to take the bus.