This is a wug.
And if there were two, there would be two ______
If you said wugs with the s sounding like /z/ rather than /s/ then congratulations! You have productive morphological capabilities. That is, when faced with a word you’ve never seen before, you were able to use your knowledge of how English works to figure out that -s is plural, and it’s voiced (z instead of s) after voiced consonants (such as g).
It’s not remarkable that an adult native speaker can do this, but when Jean Berko Gleason invented the wug for a test in 1958, she demonstrated that children can also do such things, and at a much younger age than was previously assumed.
Berko Gleason’s work is admired for its elegance and importance to the field, but many linguists are also fond of these little critters that she created. They’ve become something of a mascot for linguists, some get wug tattoos, and they appear on the International Linguistics Olympiad page.
They never fail to amuse me.
[Image is from McMaster Linguistics - a cached Geocities blog (how retro) but it’s originally from one of Berko Gleason’s papers]