I made research on gyaoppi based duck pets. There are three main families:
Guwappi duck, found in duck shell or oval shell, detailed in this page:
Standart gyaoppi duck, evolutions vary on care
Duck egg is mottled
There is no snack option, just food/water
Turn/card guessing games
Sleeping has night background
Weather options for hat, umbrella, shelter (for thunderstorm)
Has poop/sickness icons
Max life varies with care
Tamakaci duck, very similar to gyoppi, with differences. Has a watch design and quite nice pocket design with protective shell and even mirror inside! Seen here:
More info:
https://www.jdresearch.com/virtualduck.htm
Standart gyaoppi duck, evolutions vary on care
Duck egg is mottled
There is snack option
Turn/card guessing games
Happy animation subtly different with a heart animation.
Sleeping has night background
No weather
No poop/sickness icon, they are shown on screen via animations, different sickness require different cure
Max life 9?
Next is my vpet karugamo, differences:
Subtly different/unique gyaoppi evolutions, mostly very similiar
Duck egg clear with letter 'D' on it
There is snack option- feeding is the most important thing, filling all food bars cause sickness
Turn/card guessing games with subtly different animations
Sleeping has asleep duck on its face snoring animation
No weather
No poop/sickness icon, they are shown on screen via animations, different sickness require different cure-exactly like tamakaci
Max life 9
There is also internationl/english version Perpetual Duck
Exactly same as Karugamoland, background is different (karugamo has water circles, perpetual has floral pattern)
Action icons are different, overall gameplay and animations are same
All three can put to sleep and get awakened any time, which is very convenient.
Nice, different evolutions , karugamoland has subtly different bits (0 yr old duckling looks quite different)
Guwappi has weather options, karugamo/tamakaci has snack and more complex feeding