Both are historical mini dramas in which a royal lead swaps with a commoner/bandit lead, resulting in them having to navigate each other's lives all the while bickering.
Both involve a commoner and a royal of opposite genders switching bodies and then being forced to navigate each other's lives, bickering and trying to swap back.
Actually they're kinda different. The only thing they share was switching. In TSP, soul. While in AFS, their face only. TSP is more comical than AFS but the latter had a wholesome plot.
