For the biological guts back story, key elements would be the need for energy and nutrients. The evolution of guts was driven by the necessity to extract as much value from food as possible. For example, the development of specialized compartments in the guts of ruminants to better digest cellulose was a key step in their back story of gut evolution.
In the case of the general concept of having 'guts', the key element could be the first time one faced fear and overcame it. That initial experience of pushing through anxiety or danger is often a crucial part of the back story. It could be as simple as a child's first time speaking in public despite being shy.
If it's Guts from 'Berserk', one key element is his origin from a hanged corpse, which sets him apart and makes his existence somewhat of an outcast from the start. Another is his time as a mercenary, where he learned combat skills and survival tactics in a harsh world.
I'm not sure exactly which 'guts' you mean by 'guts back story'. However, if it's in a general sense of someone having the 'guts' (courage) and their back story related to how they developed that courage, it could be that they faced a lot of difficult situations in life. For example, they might have had to stand up to bullies when they were young, and through those experiences, they gradually built up their inner strength and 'guts'.
One key element is the wealthy setting. The 90210 zip code represents luxury. Another is the high - school aspect. The characters' experiences in school, like cliques and popularity contests. Also, relationships play a big part. There were romances and break - ups among the characters.
One key element is the nuclear apocalypse that destroyed Earth. Another is the Ark, the space station where the survivors were living. And of course, the 100 delinquents being sent to Earth.
One key element is the different races. Their relationships and power dynamics play a big role. Another is the political situation, with various kingdoms and factions. Magic is also a key, as it affects battles and the balance of power.
One key element is its evolution from Gastly and Haunter. Another is its connection to shadows and darkness. Also, its mischievous nature is important.
The key elements are the Smurfs themselves, their forest village, and Gargamel. The Smurfs' unique characteristics and their village setting are important parts of the back story, and Gargamel as the main villain.
One key element is his desire for power. Bowser wants to rule the Mushroom Kingdom. Another is his rivalry with Mario. Their battles are a big part of his story. Also, his relationship with Princess Peach, as he constantly tries to kidnap her. His army of minions is also an important part of his back story as they help him in his evil plans.
One key element is Tony Soprano's dual life. He's a mobster but also a family man. Another is the power struggles within the mob. There are different factions vying for control. Family loyalty, or the lack of it in some cases, is also a big part of it.
One of the key elements is my love for music. Since I was a child, I've been drawn to music. I would listen to all kinds of music, from classical to rock. This love for music has been a constant in my back story. It has given me an emotional outlet and also influenced my taste in other aspects of life.
One key element is his origin on Titan which was in crisis. Another is his radical solution for population control. Also, the rejection of his idea on Titan which pushed him towards a more extreme path.