The viewer is required if you want to see the couch gag in virtual reality, but if you don’t have a Google Cardboard Viewer, you can still view the couch gag through the Google Spotlight Stories app.
A Google Cardboard Viewer: Knoxlabs made limited edition Simpsons Google Cardboard viewers, however, you can view the couch gag with any Google Cardboard viewer.
Google Spotlight Stories app for iOS or Android installed.
It lacks the 3D-like virtual reality experience, but you’ll still get a 360 view of the scenes, and the jokes are just as funny in 2D.