Undertale Switched Up is a multiverse of AUs where a new character is added, or a canon character's role is swapped with someone else's (for example Asriel's role swaps with Mettaton's role). There are not hundreds, but thousands of AUs in this multiverse that can be happy, sad, enraging, or any other emotion! They can be really messed up, or creative. Some already existing AUs are in this multiverse, but some are still waiting to be created. As this articular said earlier, some existing AUs are in this multiverse, like Underswap or Underfell. One of the main keys in this multiverse is you can create, or destroy. The "Create" part this where Ink Sans comes in, he will help discovers make AUs. But Error Sans, he helps discovers create a messed up AU, or even DESTROY a one they made.