The Warner bros used to be explorers and found and entrance to Hollow Earth and met the Looney Tunes, they thought the World wasn't ready to hear such a theory and to prevent them from going to the Looney Asylum, they said they were cartoons.
Most Hollow Earth theories suggest an inner sun to keep Inner Earth lit, but in reality there is a giant shield at the center, which the Warner Bros incorporated in their logo, sunlight comes in from the poles at hits the shield since the shield is tilted a bit on the Z axis, reflecting the sunlight and lighting the inner shells.
The Looney Tunes are filmed by WB, you are not watching a cartoon, it is real footage of an interterrestrial race enslaved(They are not treated badly just owned by WB that is all) with the logo stitched on them, to keep track of them.
The physics are different because of the way the atmosphere of Inner Earth, making the beings stretch and regenerate.
They have found a way to connect to our internet so that is how they know about Michael Jordan.
Looney Tunes: Back in Action is set in future events were Looney Tunes are now free and are living peacefully on the surface world and interact with Humans and have brought their culture with them such as Acme.
Here is a diagram of Looney Land:
