Piglet sees what appears to be everything smaller as he grew, when really, he's wearing special goggles which make everything from his viewpoint appear far away, so it would appear as if he got bigger.
Example of:
Reverse Telescopic Vision
Piglet sees what appears to be everything smaller as he grew, when really, he's wearing special goggles which make everything from his viewpoint appear far away, so it would appear as if he got bigger.
