Wugs have endured into the 21st century. Wugs were invented in 1958, by Jean Berko Gleason. Gleason described them to an unprepared world, in her paper “The Child’s Learning of English Morphology,” Word, vol. 14, 1958, pp. 150-77.
Wugs are what showed that little kids are savvy about about making plurals. The Wug Test showed a drawing (reproduced here) of a wug and then a drawing of two wugs, and asked:
This is a wug.
Now there is another one.
There are two of them.
There are two ______.
Nowadays wugs turn up in unexpected places.
There are wugs on mugs.
There are wugs (of a sort) as rugs.
And there are wugs in Wales: