TV Tropes describes this as a comedy device where a character's underwear—often featuring goofy prints—is accidentally exposed for embarrassment.
In many health-focused articles, "wet panties" refers to moisture caused by natural biological processes. wet cartoon panties
Experts at Verywell Health note that watery discharge is normal during ovulation or pregnancy, though changes in color or smell should be checked. TV Tropes describes this as a comedy device