Harvest Moon: Animal Parade's Maya. She's absurdly perky and cutesy. If she's a grown woman, why does she feel free to act like that? Then I looked at her family and realized why: Her parents are still lovey-dovey with each other even though they've been married for more than twenty years. They have a perpetually cheerful and optimistic outlook on life, so of course she'd pick it up from them!
A possible bug in the original: Eve, unlike every other wife, suffers a relationship penalty instead of a bonus when you go to bed with her. However, on second look, this makes perfect sense: she has attachment issues and has trouble maintaining a stable relationship, even with people she loves, resulting in a tumultuous marriage that takes a lot more effort to make work.
In Harvest Moon: A New Beginning, both Amir and Yuri's hearts are invisible unless you start dating them. It makes sense for Amir to have an invisible heart, since he's a special bachelor in Grand Bazaar, but why is Yuri's heart invisible? Because she's a very quiet, timid person—in other words, she doesn't wear her heart on her sleeve!
Or worse—in AWL you can marry fourteen-year-old Lumina. Now you're allowed to be a real babynapper.
For the PS2 version of AWL, Lumina was aged up to 18, though.
In Harvest Moon 64 the main character is the grandson of the protagonist in Harvest Moon for the SNES, and each of the five eligible bachelorettes are implied to be the granddaughters of the eligible bachelorettes in that game. If we assume the main caharcter in Harvest Moon married one of the bachelorettes in that game, then when playing Harvest Moon 64 you have a 1 in 5 chance of marrying your cousin.
In Magical Melody, when a typhoon comes in the middle of summer (or snowstorm in winter), you are stuck in the house with your pets until the storm escalates once you return to bed the next day. When you check your records, Jamie somehow managed to deliver crops that previous day despite time does not pass when you're indoors, and you cannot go out, rendering you to have to skip the day. Jamie must be one hell of a Determinator just to ship his/her crops.