So got to get the plot moving somehow, also some insights into why Don feels a particular need to help Vanessa

As Vanessa ran blindly into the sewers as fast as six of her eight limbs could carry her (The first two functioned as her arms) Don ran after her.

"Vanessa!" He called out "Vanessa wait! Don't run into the sewers! It's dangerous! You don't know what you might encounter!"

"It's hopeless!" Vanessa cried "It's absolutely hopeless!"

"It's not hopeless!" Don called after her "There is still a possibility I can find a cure you just need to give me time!"

Vanessa stopped where she was and just stood where she was and cried.

"Your brother won't let me stay..." She sobbed "...And I know why, it's because I'm too ugly...If I stay I fear he'll pop me like a zit!"

Don felt incredibly angry at Raph for making the poor girl feel this way, "We'll...We'll talk to him Vanessa, I'm sure Master Splinter will talk to him...And possibly do more than that..."

"Why..." Vanssa said as she rubbed her weepy eyes "...Why did I have to turn into a spider of all things? I know why, cuz our apartment won't allow pets..."

Don remembered the 'pink ooze' he knew he didn't have a chance to study it, but it seemed a hard and fast rule that it only reacted to the last animal you touched, so it wouldn't matter if she caressed a pet before leaving if it was still the spider she stepped on when she touched the ooze if this new blue ooze operated on the same principle as the pink ooze.

"Vanessa..." Don cooed soothingly, remembering that this girl was only twelve years old "...Remember it's not your fault..."

He came close to her head.

"Vanessa," He sighed "I'm not going to give up on you, because...I was once...Maybe not the same situation as your's but I was in a position where I needed my family not to give up on me..."

Vanessa looked up curious

"I once got a secondary mutation from a new type of Mutagen entering my system..." Don said "...My secondary mutation turned me into a giant and mindless beast, that attacked everything I saw..."

"You mean like rabies?" Vanessa asked

"Yeah, pretty much." Don had to admit the comparison was pretty apt "Anyway, because I had been reduced to a mindless animal..My brothers had to make a deal with one of our enemies in exchange for a cure..." Don stopped mid-sentence because he heard the sounds of footsteps and soft conversations appraoching.

"Listen..." Don said quietly "...Sewer workers...We got to hide before they see us..."

Since Don was pretty familiar with the sewer workers patterns, he led Vanessa down a tunnel he knew the sewer workers weren't about to head down.

"So did you hear about those Arkham Nuts coming to the Big Apple?" One sewer worker said to the other

"Don't tell anyone I said this..." Said the other "But I swear I saw them last night entering the Proteus Inc Headquarters!"

"Proteus Inc huh?" Said the first one

"I've heard Judith Noble is getting pretty desperate to complete some of her life's work..." The other one said "...Got to be pretty desperate to be willing to hire those lunatics to help you with your research..."

Don and Vanessa exchanged glances, if that didn't sound like a potential clue they didn't know what was!

I remember a converstion with a fanfiction colleague on the subject of the 80s and 2012 cartoon Mutagen, kind of don't like one she did where a guy turned into a Bull from eating a steak, kind of like the Animorphs rule that it has to be DNA from a living animal (Or in the case of Vanessa's pider was alive for a split second she was touching the Mutagen, I mean the 80s cartoon always used living animals with Shredder always going to pet shops or zoos when he wanted to create more mutants (I mean kid's show in the 80s/Early 90s probably didn't want to upset kids by adressing that cute animals are where meat comes from) but for another reason, I often deprive my protagnanists of pets because it would be 'too easy' a source of mutation an animal they chose to live with