doofus
doofi
doofi
doofam
doofa
doofae
doofarum
doofis
doofas
doofis
HEY! You haven't been here long enough to be so authoritative-like! You gotta be here from the last century to qualify as a genius.
It's been a while but...
alumnus and alumni
alumna and alumnae
So wouldn't the plural of dufus (being masculine) be dufi? And girls who are dufuses would be dufa and dufae.
Mica, mica, parva stella!