Note: The timeline of the series is a bit hazy, as the entire setting is in an Ambiguous Time Period. As such, this list will not attempt to attach exact years to anything, save when the series itself does so.
- Fifty years before the "present", the future Mother Superior establishes a convent in a previously-abandoned building, working on it with the help of Froggy Nun's grandmother and the mother of the future Pancake Nun, among others.
- The nuns notice a young girl living in a tent on the convent grounds, drawing extremely detailed sketches of everything around her. They invite the girl to live in the convent, and she becomes the Artist.
- In a church in a large city, a young orphan with a brilliant mind and stoic disposition lives with the monks. She's interested only in reading books and not the physical activity the young men enjoy. One day, the Artist visits the church with several ducks and her dog and meets the girl, and they get along exceedingly well.
- A priest from this church and the girl eventually depart for a rural convent. The priest is known today as The Father, and the girl will grow up to be the Star Nun.
- Having grown up, the Artist decides to leave the convent for her own reasons. She leaves behind a massive artistic legacy, as well as a monumental impact on the Star Nun.
- A somewhat violent girl appears at convent. After the older nuns (Mother Superior in particular) calm her down and teach her to smile, she eventually becomes Smug Nun.
- A starving young girl is found outside the convent, with no apparent family. The nuns take her in. She will grow up to be the Strict Nun, and immediately develops a heated rivalry with Smug Nun, who feeds on this dislike.
- A young girl obsessed with rabbits arrives at the convent. She will grow up to be the Bunny Nun, but not before a rough transitionary period where she tries to hypnotise the convent’s ducks into acting like rabbits.
- The owner and sole employee of a failing donut shop is found unconscious from exhaustion with her young daughter near the convent, and they are taken in and cared for. The donut shop owner makes the difficult decision to leave her daughter in the convent's care, as she is unable to provide for her on her own. The daughter becomes the Hungry Nun.
- The donut shop owner is able to focus on rejuvenating her business, and by the present, it is far more successful.
- Eleven years before the "present", a baby girl is abandoned on the steps of the convent. She is taken in by the convent, and the Strict Nun becomes her primary caretaker. She becomes the Clumsy Nun.
- A couple of years before either of them actually join, roughly eight years before the "present", the future Sheep and Froggy Nun (the latter just a newborn at this point) visit the convent with Froggy's father. It's implied that Froggy's mother died in childbirth, but it's unknown if Froggy's grandmother is still alive at this point.
- The Artist returns to the convent and drops off her young daughter, the Spicy Nun, to be educated by the nuns. She and the Clumsy Nun become fast friends.
- A girl with terrible eyesight arrives at the convent. The nuns get her a pair of glasses, making her the Glasses Nun.
- Some time after the deaths of his wife and mother, the Frog Nun's father drops her off at the convent. She is initially overcome by homesickness, but the arrival of the Sheep Nun gives her someone to rely on. The two girls become inseparable.
- The comic arrives at the "present".
