One common theme is friendship. Given that Discord has a complex personality and Luna is a princess, their friendship development is often explored. For example, how they learn to trust and rely on each other.
The theme of redemption can also be present. If Supernova is initially a character with some flaws or has made mistakes in the past, the fanfic might show how Luna helps Supernova to redeem themselves. This can create a deep and meaningful story arc, as Supernova grows and changes throughout the course of the fanfic.
Well, there's a fanfic called 'Luna and Discord: An Unlikely Friendship'. In this one, it delves into how their friendship forms despite their differences. It shows how Discord's chaos and Luna's calmness can complement each other in various situations. There are also some fanfics that are part of a series, like 'The Luna - Discord Chronicles' which unfolds their story over multiple installments.
Another theme is redemption and guidance. Luna has a past she's trying to overcome, and in many fanfics, she helps the reader while also finding her own path to redemption. It's about two characters growing together in different ways. For example, in some stories, the reader might be lost in Equestria and Luna guides them, while at the same time, the reader's presence helps Luna face her inner demons.
One common theme is friendship. Since Spike and Luna are from different parts of Equestrian society, their friendship can be explored in many ways. For example, how they bridge the gap between a young dragon and a princess of the night.
Another theme is friendship. Even as a baby, Luna is shown forming bonds with other ponies or characters, like how she might interact with her sister Celestia in a more innocent and playful way. And these interactions help shape her future relationships. For example, in some fanfics, her early experiences with friendship teach her important values that she carries into her later life.
A common theme is friendship. Despite their different personalities, they often end up becoming friends in fanfics. Another theme is magic. Since both are associated with magic in the My Little Pony world, their magical abilities are often explored. For example, they might combine their magic to defeat a common enemy.
Redemption is a very common theme. Luna often has to prove herself after her return, making up for her past actions. For example, in many fanfics, she tries to regain the trust of the ponies in Equestria.
A common theme is identity. Since Luna is in a human form, she often has to grapple with who she is now compared to her pony self. Another theme is acceptance, both her accepting her new human form and the humans around her accepting this strange new being in their midst.
One popular MLP sad Discord fanfic could be 'The Lonely Spirit of Discord'. It delves into Discord's feelings of isolation even after his reformation. It shows his struggle to fit into the harmonious world of Equestria, which makes it a rather sad read.
The uniqueness of MLP Discord tickle fanfics is that they often blend the fantastical elements of the MLP world with this rather specific and somewhat silly concept of tickling. Discord, being a powerful and unpredictable character, his experiences with tickling can lead to all sorts of humorous and unexpected situations. It can also show a more vulnerable or friendly side of Discord that we might not see as often in the main series. Moreover, the fanfic authors can use tickling as a tool to create new story arcs and character developments that are different from the traditional MLP narrative.