When Suneo found a cat dumped in the vacant lot, Gian said he couldn't keep it because he had a dog. Suneo couldn't because he had pure-bred cats. Shizuka couldn't because she had a canary. And Nobita couldn't because he had his mom.
On April Fools' Day, Nobita tricked Gian by telling him Shizuka liked him, but Gian then tricked him back by saying it wasn't April Fools' Day and beating him up for lying. After that, Nobita was tricked by Suneo and Shizuka. To let him get revenge, Doraemon gave Nobita the "Lie Machine" (うそつ機), which makes everyone believe any lie he tells.
Source: うそつ機, 1973 (manga)
When Doraemon left Nobita for the future, Suneo told Nobita that he'd seen a Tsuchinoko on April Fools' Day, while Gian told him that he'd seen Doraemon. Upset by this, Nobita drinks the "800-Lies Potion" (ウソ800) Doraemon saved for him. It makes anything he says into a lie, letting him get revenge on Gian and Suneo.
Source: 帰ってきたドラえもん, 1974 (manga)
Another April Fools', Gian told Nobita that he was going to give him cake, while Suneo told him he would give him his stamp collection. Nobita uses the "Thousand-Needle Badge" (ハリ千本バッジ) to force them to keep their promises, but this backfires when Shizuka tells him that his house is on fire.
Source: ハリ千本ノマス, 1975 (manga)
Nobita was fooled by Suneo again on April Fools' when Suneo gave him a fake treasure map.
Source: 化石大発見!, 1976 (manga)
When Nobita thought that aliens were going to invade, Dekisugi was the only one who would believe him. But he then told Gian and Suneo that it was April Fools' Day and he was only pretending to fall for Nobita's "lie".
When Nobita's friends used the "Pet Pen" (ペットペン) to draw the pets they wanted, Gian drew a parrot, Shizuka drew a koala, and Suneo drew a panda.
Source: ペットペン, 1984 (manga)
A different time, they used "Pet Paint" (ペットペンキ) to turn rocks into pets. Gian still drew a parrot, while Shizuka drew a panda. Suneo drew many little birds, but was crushed by their weight because they were made of rock.
Source: ペットペンキ, 1983 (manga) [recolored version shown]
What do Nobita's friends want to be when they grow up?
Shizuka wants to be a flight attendant, nurse, or kindergarten teacher (職業テスト腕章, 1981 manga story). Because of this, Doraemon invited her to be a flight attendant when Nobita ran his own airline with the "Tricycle Plane" (三輪飛行機). Another time, she said she wanted to be a diplomat (Nobita's Three Visionary Swordsmen, 1994 manga).
Source: のび太航空, 1982 (manga)
Gian says many times that he would like to be a singer (職業テスト腕章, 1981 manga story), but he has also mentioned wanting to be a model.
Source: きせかえカメラ, 1974 (manga)
Suneo usually says he wants to be a fashion designer. He has also expressed interest in being a director (のび太放送協会, 1975 manga story).
Source: きせかえカメラ, 1974 (manga)
And Nobita? We've looked at his career aspirations before!
Suneo keeps many pets, often bragging about his purebred Siamese cats. One of his cats is named Chiruchiru.
Source: ペットそっくりまんじゅう, 1976 (manga)
Another is Anna, who once found a diamond Suneo's mother had lost.
Source: 野生ペット小屋, 1983 (manga)
A third cat that has been mentioned is Catherine (Nobita and the Galaxy Super-express, 1996 manga). The Doraemon Fukayomi Guide (ドラえもん深読みガイド, 2006) speculates that she is the un-named cat Suneo has taught to do tricks.
Source: ペッター, 1986 (manga)
Suneo's family has a koi pond in their yard.
Source: 空とぶさかな, 1971 (manga)
And they have a tank of tropical fish.
Source: ツバメののび太, 1981 (manga)
When Nobita used the "Animal Observation Case" (動物観察ケース) to "keep" wild animals, Suneo tried to outdo him by buying an iguana.
Source: ツバメののび太, 1981 (manga)
Suneo also has a myna bird who is trained to speak.
Source: 九かんマイク, 1981 (manga) [recolored version shown]
He owns a dog as well.
Source: お化けたん知機, 1970 (manga) [recolored version shown]
On New Year's, Nobita always falls over trying to fly kites and gets his face marked with ink from losing at hanetsuki (Japanese badminton), so Doraemon prepares bandages and warm water for him beforehand.