This kind of situation could cause various reactions, depending on the context and the audience. Some might find it inappropriate or offensive, while others might view it differently.
I have no definite knowledge on this. It could be a term used in a niche manga or related fan community with a special meaning. But without additional details, it's difficult to determine the exact nature of the connection.
Plastic shrink art is a creative process where plastic sheets are heated and shrunk to form various shapes and designs. It can be related to cartoons when used to create characters or scenes from them.
It could be part of the story to create a peaceful or funny moment. Sometimes, a sleeping character adds an element of surprise or sets up a future event in the cartoon.