Yes, in fanfiction, the possibilities are endless. Ash could be depicted as having a great singing voice. Writers often take creative liberties in fanfiction to show characters in new and unexpected ways, so it's very likely that there are fanfictions out there where Ash sings.
Pokemon porn comic is neither legal nor ethical. It's a form of content that is considered offensive and against the law. Such material can cause harm and has no place in a civilized society.
Pikachu is a very likely candidate. It's Ash's most iconic Pokemon and has a deep bond with him. Whenever Ash is in trouble, Pikachu often steps up to protect him.
Savage Ash is often more independent. The original Ash usually travels with friends and follows the traditional path of gym battles. Savage Ash, on the other hand, might go off on his own, not caring much about the established rules. For example, he could skip gyms and focus on conquering powerful wild Pokemon.
One possible fanfic could be that Ash accidentally sits on a hot Pokeball which causes his butt to be on fire. He then runs around in a panic while his Pokemon try to figure out how to put the fire out. Pikachu might use Thunderbolt but that just makes things worse by electrifying Ash as well.
There are also often appearances from various Gym Leaders. They can serve as either allies or rivals to Ash. For instance, a Gym Leader might challenge Ash to a battle to test his newfound power, or they could join forces with him to take on a greater evil that threatens the Pokemon world.