From Nookipedia, the Animal Crossing wiki
Cranky villagers (also called Grumpy villagers) are male villagers in the Animal Crossing series. The name is a direct reference to the meaning of cranky; someone who is irritated or annoyed easily. They are considered the male equivalent to the snooty villagers.
The cranky characters can seem quite bitter and out-of-touch with social trends, making them generally unpopular with the peppy villagers. They are all deep-voiced (unlike every other villager) and many have frowns. They usually go to sleep at 5:00 a.m. and wake up at 10:00 a.m. each day. When trying to enter the house of a cranky person before they wake, the player is greeted with an angry letter explaining that they are sleeping, "I'm catching some Z's right now, wake me and REGRET IT". They usually spend half of the day in their houses and half of the day out.
Cranky villagers find it easy to get along with snooty villagers and other cranky villagers, usually discussing trivial things such as food and the problems with unhealthy food. They get on with normal and lazy villagers most of the time, but can offend, and therefore annoy them quite easily if the wrong things have been said. They find it difficult to get on with peppy and jock villagers, who cranky villagers claim are mucking around. They can occasionally can be good friends with a peppy villager. Thus, conversations between a cranky villager and a villager of one of these types will result in one of them depressed and occasionally cranky villagers will tell the player that things are getting boring so they are considering spreading rumors about another animal and 'watching the fun'. The usual response from either of the personalities is to call them an 'old man' or 'grandpa'.Although they may appear unfriendly, if the player talks to them, does errands for them and sends them letters for long enough, they will eventually begin to open up and will be more friendly with the player. In Animal Crossing, a cranky character will often speak to the player about their niece after becoming friends. Also, in City Folk, they may say this to another cranky villager.
In Animal Crossing: New Leaf, the cranky characters' unfriendly demeanor has been toned down, thus making them easier to befriend.
Below are some (not all) quotes made by cranky villagers.