What even is the purpose of these?
Anyway, wow it's already December.

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Taken from Horus Urusei Eye, a website that was dedicated to hosting Urusei Yatsura official art but has been offline for quite some time now. The site also hosted a bunch of other things such as art of other Rumiko Takahashi works, TV show theme songs, and the host's own weird fetish edits. These have not been preserved as well as the UY aspect of the site, so they may as well be lost to time.
If anyone has a larger backup of Horus Urusei Eye or has found it under another domain, please PM me!

They're plastic underlays used when writing on paper (下敷き)
presumably to make it easier to write without a table or hard surface.

https://www.asahi-net.or.jp/~ty5s-kmr/gd04a.html

Base +4, Floripes +38

And primarily promotional material. We take for granted how easy it is to disseminate information today, but in the 80s it was pretty damn hard to inform the public about stuff like new TV shows coming out. Animation studios would give stuff like this away in magazines, or with school supply kits, or with meals...just about anything.

Base +6