It's been a while since I've drawn anything about this goober and he reeaaallly needed a proper reference and updated design. Now Yakko has a proper critter hanging out in his mindscape screeching at early hours in the morning :>
The lore for this goober has definitely changed immensely. Instead of the infection on Yakko being intentional, it was a complete mistake. When the Warners made their way to a space station for a new episode and found no one there, they decided to explore for a bit to try and figure out what happened or find something of use. Unfortunately for Yakko and Shroom, the eldest sibling happened to be passing by one of the vents the Parasite was struggling to stay in.
He fell right onto Yakko's shoulder and accidentally scratched his neck with their tail out of surprise when he whipped his head around, resulting in the original parasite's death since they spread their DNA to a new host.
It took a good few weeks for the new version of Shroom to emerge, and the entire time the Warners had to watch their brother be completely bedridden for a reason they didn't understand. It was actually the reason they sought out help from other beings they knew that could make sense of things, and by the time they came back, Yakko seemed better somehow.
He thought it was just over with, that the sickness had just passed, but some things started going incredibly wrong around the studio. Toons were going missing, Yakko started to space out more than usual, and he always felt a bit sick.
Essentially, when these parasites form, they will usually run off of only two things: Fight or Flight. More often than not, it's Fight. Without the siblings being there, they were thankfully spared from seeing Yakko's body being taken for a joyride to gather food for his new mental roommate. The worst part about this is, even with Yakko being a toon, these parasites are always merged with the brain of their victim when they form, and removing them would kill both of them.
This does, of course, also mean that with how Shroom's species works, they're able to harness any abilities their host may have. So Shroom himself is able to use Toon Force. Thankfully, with the help of those strangers, and some help from Yakko's siblings, they managed to figure out the issue and got the parasite to agree to their terms, deciding to live with them instead of against them as they made synthetic versions of what Shroom needed to survive.
Now the two of them help any new, or older, infected pairs they find, trying to help them grow closer or use a method of separation for the safety of either by using a stone from the home world of these parasites. (It essentially makes them feel extremely ill and leaves them immobile for a long while with just a single touch to the host or them.)
