In the original result of the Wug Test, children consistently produced wugs for the plural. However, plurals other than the standard wugs are sometimes used humorously, including wuggen (by analogy with oxen), weeg, and wuggi (by analogy with Latinate plurals).
Wiktionary says
Wuggi sounds nice. Huggy wuggi :3
Wugopodes
That's Greek to me
:3c
Wuggingtons
Wuggi is the first thing that came to muh brain