I know! There are a lot of kids that have Tamagotchis so here is the info and I asked them the question so I will give EXACT info. (that I know of anyway) I have added extra interesting details that might make your speech paper sound more exciting. I have added the most popular into groups of the stages, baby,toddler,teen and adult (I also added another colum on some secret characters on the current tamas)
Most Common: Kuchipatchi
Least Common:Hanatchi
Most Popular:list-
Baby:
babychi (boy & girl)
toddler:
Marutchi (some people think it looks like Pac-Man)
Kinkoamonchi (my friends call him "the nut dude")
Teens:
Ichiogotchi ("ichio" means strawberry, also known as the strawberry dude)
Hinotamachi ("Hino" means fire,also known as the fireball guy)
Young Mimitchi (some people mistaken Young Mimitchi with Young Mametchi, differance? Young Mimetchi is popular and the other one is not)
Onionchi (also known as the onion dude, it made two of my friends cry whebn they got it! LOL!)
Adults:
Mametchi (one of the first characters)
Mimitchi
Kuchipatchi (some people think this character is related to the duck, mistaking for Kiwichi for some people and Kiwichi is VERY unpopular,one of the first characters)
Memetchi (popular for cuteness)
Tarakoachi (this character had a HUGE make-over since the first tamagotchi,one of the first characters)
Hanatchi (some people say it has bad allergys)
Robotchi (belived to be made out of a robot that fell apart)
Masketchi
Gonzarutchi (the ninja dude)
Odlies:
Okokitchi
Ojitchi
Secret Character:
Oyajitchi
Nazochi
Least popular:
Puchitchi
Shiropuchitchi
Hitodetchi
Kuribotchi
Prepelloretchi
Ufotchi
Ringotchi
Young Mametchi
Nikatchi
Hinatchi
Furawatchi
Toratchi
Kaelutchi
Hatenatchi
Marumimitchi
Cho Himetchi
Pyonchitchi
Ginjirotchi
Pochitchi
Nyorotchi
Kusatchi
Takotchi
Kiwitchi
Debatchi
Dorotchi
Kabutchi
Urutchi
Hiratchi
Zuccitchi
Butterflytchi
Flowerchi
That is all I know for know. Use any info from that you need.