Generic Helpers

Some helpers are the same for every type: get a component or add it, pick a random entry from an array. A generic method writes them once, with the type as a parameter T that each call fills in:

public static class Helpers
{
    public static T GetOrAdd<T>(this GameObject go) where T : Component
    {
        if (!go.TryGetComponent(out T found)) found = go.AddComponent<T>();
        return found;
    }

    public static T RandomItem<T>(T[] items)
    {
        return items[Random.Range(0, items.Length)];
    }
}

Rigidbody body = crate.GetOrAdd<Rigidbody>();
Color paint = Helpers.RandomItem(colors);
GameObject enemy = Helpers.RandomItem(enemyPrefabs);

where T : Component is a promise about T, and it decides what the method may do with it. AddComponent only takes components, so without the constraint the compiler refuses go.AddComponent<T>(); with it, any component works, Unity's Rigidbody or your own scripts. The constraint also gives you every member of Component on a T, such as .transform and .gameObject. A crate that already has a Rigidbody gets that one back, and nothing is added.

RandomItem has no constraint, because it never touches T: it works for colors, strings and prefabs alike. You rarely write the type at the call: from colors, a Color[], the compiler works out that T is Color. A method that takes IEnumerable<T> instead of T[] accepts arrays and Lists both, including the arrays FindObjectsByType<T> returns.