The potions gave their s symptoms of drunkenness. Initially, they took the potions for fun. As the drunkenness took effect, their capacities for rationality waned. Soon they assumed that they now had authority equal to the real royals.
It didn’t take long for the afforementioned real royals to see them fooling around. Quickly, they understood what was happening &, entertained by the guards & their behavior, let them pretend to be the royals for a day, even giving the fake Celestia a fake throne to sit on, while the court pretended to follow the whims of the fake four, waiting for the potions to subside.
I can understand that the potion changed the guard and gave him Celestia’s body. But why did he replace the real Celestia? Or in this case, Celestia never existed?
This… actually explains a lot. Where do you get these details from?