Another theme could be support. The piggyback situation might symbolize one character supporting the other, either physically or metaphorically. It can be in times of trouble or just in a casual, affectionate moment. In many of these fanfics, it also might explore their shared history and how that has led to this unique interaction.
Friendship is often a common theme. It shows the close bond between Bucky and Steve, with the piggyback aspect adding a touch of playfulness or a sign of trust in their relationship.
Another common theme is loyalty. They are extremely loyal to each other. In some fanfics, they'll go to great lengths to protect one another, even if it means going against the whole world. It's a very powerful aspect of their relationship that writers often explore.
I'm not sure about specific 'bucky steve piggyback fanfic' but you can try searching on fanfiction websites like Archive of Our Own. They usually have a wide variety of fanfics related to different characters and scenarios.
One common theme is friendship. Bucky and Steve have a long - standing friendship, and the addition of the Reader often explores how new friendships are formed and how they all support each other. For example, in many fanfics, they might help the Reader deal with personal problems while strengthening their own bond.
Common themes in these fanfics include perseverance. They persevere through difficult situations together. There's also the theme of acceptance. Steve accepts Bucky for who he is, even with his past and his flaws. And the theme of love conquering all is very present. Their love is shown to be strong enough to overcome any obstacle, whether it's from the outside world or their own internal struggles.
One common theme is protection. Bucky and Steve often see Tony as someone who needs safeguarding, whether it's from physical threats during missions or from the emotional harm caused by his past. For example, in many fics, they'll stand up for Tony when others in the Avengers question his motives.
One common theme is loyalty. Steve and Bucky have a deep loyalty to each other that is often explored. For example, in many fics, Bucky will go to great lengths to protect Steve and vice versa.
Friendship and love are also big themes. The relationship between the three can range from deep platonic friendship to romantic love. In some fanfics, they struggle to define their feelings for each other. They support each other through tough times like battles and personal crises, which shows their strong bond.
Friendship is a very common theme. Despite their differences, they come together and form a strong bond. Another theme is redemption. For example, Bucky might be seeking redemption for his past actions, and Tony and Steve play a role in that process.
One common theme is loyalty. Their loyalty to each other is a big part of their relationship and is often explored in fanfics. For example, Bucky always being there for Steve, and Steve never giving up on Bucky.
One common theme is friendship. The OC often becomes a part of the friendship between Bucky and Steve, either strengthening it or causing some temporary rifts that they have to overcome. Another theme is redemption. Bucky, with his complex past, may find a new path with the help of the OC and Steve.