Fates Disrupted

Fates Disrupted is an AU where characters switch roles. Some personality traits remain the same, but most things about them are swapped.
==About the AU==
Fates Disrupted takes place in a parallel timeline where the monsters are free to choose their environments. One day, Mad Dummy and Flowey get together for a nice conversation about how their lives would be interesting if they could switch places with one another, but Mad Dummy realizes "Flowey" is acting strange. It turns out Gaster had disguised as Flowey, and now Mad Dummy has become the first to "shift" forms. Slowly, everyone in the Underground starts "shifting" forms, including Sans, Undyne, Mettaton, and even Chara. But before disappearing from the timeline, Gaster "shifts" himself. Parts of the characters' personalities swap (for instance, Mad Dummy now knows how to speak to the player directly, but still retains his habit of repeating things three times, calling people names, and other key features about him.
==Canon Swaps==
Mad Dummy is in Flowey/Asriel's role.
Napstablook is in Toriel's role.
Snowdrake is in Napstablook's role.
The Annoying Dog is in Sans' role.
Temmie is in Papyrus's role.
Chara is in Gaster's role.
Bratty is in Undyne's role.
Catty is in Alphys's role.
Goner Kid is in Monster Kid's role.
Chilldrake is in Mettaton's role.
Mettaton is in Asgore's role.
The Ruins Dummy is in Chara's role.
Snowdrake's Dad is in the Mad Dummy's role.
Snowdrake's Mom is in the Ruins Dummy's role.