Hey I really like that crossover too, here is a fanfiction I wrote about it:
Once upon a time, Ben 10 decided to team up with Danny Phantom, so he called him up one day and he was all like "I fucking hate niggers" and Danny Phantom was like "I also hate niggers we should team up" and so they did. Only I have no idea who Danny Phantom is because I'm not autistic enough to know that and I don't really care and I can't be fucked to google it right now so I'm going to imagine him as a giant emperor penguin with fucking razor sharp teeth and rocket boots because that would be fucking rad.
So anyway Danny Phantom the Penguin shows up at Ben 10's house one day and Ben 10 opens the doors and immediately gets kicked in the nuts so hard he temporarily becomes Ben 5. And he's rolling around on the ground clutching his balls and screaming about how he hates niggers and Danny Phantom Penguin kicks him in the balls again. And then Ben 10's sister whose name I don't know because I've never actually seen an episode of Ben 10 comes in, and she's all like "what the fuck fag" and kicks him in the balls because it's funny to do that.
Now Ben 10 is like Ben 2.5 and he is screaming about niggers in a really high pitched voice because he got kicked in the nuts. Meanwhile his sister and the penguin are laughing their asses off. Then the penguin tells Ben 10's sister to suck his dick and she does because according to what I've seen on the internet she is kind of a whore. And then the penguin tells Ben 2.5 to suck his dick and he does because he's a fag, only after he's finished he wipes the cum off his chin and says "no homo" so that made it totally not gay. And then he reminded the penguin that he had forgotten to say "no homo" so that meant that he was actually gay, but the penguin says no it's only gay if you suck a dick not if you get your dick sucked. And Ben 10's whore sister was all like "yeah Ben 2.5 didn't you know that?"
And Ben 10 is all like "My name isn't Ben 2.5 it's Ben 10 you stupid cunt whore" and she laughed and said "no fag your name is Ben 2.5 because that's what you have tramp stamped on your back" and Ben turned around and saw that it was true, his tramp stamp tattoo actually said "ben 2.5" and not "ben 10". "I don't remember getting that tramp stamp tattoo and anyway they wrote the wrong name so I am going to go to the tattoo place and get it changed" and his sister said "I really don't give a shit what you do retard" and the penguin said "Yeah fag now go away I am going to bang your sister for a while."
And Ben 2.5 went to the tattoo place and threw open the door and said "Holy fuck I hate niggers!" and there were a bunch of niggers in there as it turned out. And they all said "gib reparations welfare ooga booga honkey" which is nigger speak for "please direct me to the railway station" so Ben 2.5 told them where the railway station was. After that they stabbed him and took all of his money lol.
And then he went to the tattoo man and said "Hey faggot this tattoo you gave me has the wrong name it is supposed to say Ben 10 not Ben 2.5" and the tattoo man said "don't call me a faggot, faggot. you are the one with a tramp stamp tattoo that has the wrong name on it." and Ben 2.5 could not argue with that logic because it was flawless.
And then Ben 2.5 said "Change the tattoo back to the right name so I can be called Ben 10 again" and the tattoo man said "sure faggot just pay me 2000 dollars" and Ben said "I don't have that much money because the niggers stole it." And the tattoo man laughed and said "yes that is pretty much what niggers do, but for now you are Ben 2.5 because I don't do this shit for free" and Ben 2.5 asked "what can you do for free" and the tattoo man said he could change the tattoo so it said ben15 :DDDDDDD but Ben 2.5 was too much of a newfag to get that joke.
So Ben 2.5 went out and made $2000 the only way he knew how: by sucking 2000 dicks for $1 apiece. and then a pony came up and said "wow you sure do love sucking dick, I have never seen anypony suck that many dicks before, at least not since I looked in the mirror while I was sucking 2000 dicks." And sure enough the pony that had walked up to Ben 2.5 was none other than Silver "holy shit I have an entire box of crackers up my ass how did those even get in there lol" Star.
And Silver "seriously there is like a jumbo box of fucking wheat thins up there what the actual fuck I don't even like wheat thins" Star bet Ben 2.5 that he couldn't suck 2000 more dicks and Ben 2.5 was like "you're on you faggot horse" and then they went off and sucked dicks until both of them died of asphyxiation. Meanwhile the Danny whatever Penguin stayed home with Ben 2.5's sister and they hung out and smoked weed and played xbox and shit. And then eventually they were like "I wonder where Ben 2.5" went and then they realized they didn't care, so they turned on the TV instead of going to look for him. And they saw on the news that Ben 2.5 and Silver "never mind they aren't wheat thins they are ritz crackers and I actually like those and now that I think about it I did put a box of them up my ass" Star had died while sucking 2000 dicks each.
And Penguin whatever Danny boy laughed and Ben 2.5's sister laughed and they went to go to the morgue to identify the body and they said "yep it's him" and the mortician asked "what would you like on the tombstone" and they both said "cheese and pepperoni" and laughed, but the mortician didn't get the joke so they explained it but he still didn't get it. and then they were just like "ok put whatever on it we don't care" so he did, and he gave them the tombstone and the body and told them to go bury it in the cemetery somewhere.
So they took the body down to the cemetery and they buried it and now to this very day you can go there, and see the tombstone that says "Here lies Ben 2.5, he was a massive cum gargling faggot who died while sucking 2000 dicks." The end.