View the full-size image against a dark background (by e.g clicking the link next to "Size:", or using custom CSS) to reveal the truth of this image.

I forgot which tag for that kind of transparent background. And do we really need to tag all of the characters?

FriendOfTheDevil said:

...

I've honestly approved this before even checking that, pretty neat.

Neiri said:

I forgot which tag for that kind of transparent background. And do we really need to tag all of the characters?

I can only think of when_you_see_it as to hint the hidden aspects of the image.

FriendOfTheDevil said:

View the full-size image against a dark background (by e.g clicking the link next to "Size:", or using custom CSS) to reveal the truth of this image.

Clicking "view original" and then right clicking and selecting "view image" worked for me.

Neiri said:

I forgot which tag for that kind of transparent background. And do we really need to tag all of the characters?

Thumbnail_surprise is the tag.