Party.giveMon stores "EGG" as a new egg's nickname (party.lua for a
gift egg, breeding.lua for the Day-Care's), and the party slots and the
other screens that name a mon through Pokemon.displayName and
displayMonName print that nickname as it is. A translated game therefore
listed its eggs as EGG, while the summary, which prints Strings("EGG")
for an egg, already said OEUF, EI, HUEVO or UOVO.
The cart does not rely on the stored nickname either: its Day-Care
writes the Japanese タマゴ there (daycare.c:1100), and GetMonData
returns gText_EggNickname for any egg's nickname (pokemon.c:3020). Do the
same in both name helpers: an egg reads as Strings("EGG"), whatever its
nickname holds, which also covers the eggs saves already carry. A
hatched egg, whose nickname is cleared, goes back to its species name.
bryanthaboi