Hisoka would be really interesting. His unpredictable and somewhat psychotic nature would create a lot of chaos in the My Hero Academia world. The heroes would be really challenged to deal with his nen abilities which are so different from quirks.
Saitama in the world of Boku no Hero Academia would be really interesting. He's so overpowered compared to the characters in Boku no Hero Academia. His simple and straightforward personality would contrast with the more complex and emotional characters there.
One idea could be a crossover where Gon and Midoriya meet and have to team up to face a new villain that combines the nen and quirk powers in a dangerous way. Another could be a story where Hisoka somehow ends up in the My Hero Academia universe and starts causing chaos among the heroes and villains there. A third idea might be a fanfic where Ochako discovers nen abilities and tries to incorporate them into her hero training.
Leorio and Yang would be quite a combination. Leorio's medical knowledge could be useful when Yang gets injured in battle. And Yang's brash and energetic personality could pull Leorio out of his more serious and studious mode. They could also have some funny exchanges about money and values, as Leorio is often concerned about finances while Yang is more about the thrill of the fight.
I think Killua and Ziva would make a great pair. Killua has his assassin background and lightning - fast reflexes, and Ziva is a former Mossad agent with her own set of combat and investigative skills. They could have some great action scenes together and also share their experiences of growing up in a world of danger and secrecy.
I think Deku would be really interesting. He could be sharing his thoughts on how he's constantly trying to improve his quirk and live up to All Might's legacy. His nervous but determined personality would add a lot of charm to the sleepover.
It's hard to say for sure, but Naruto could be a very strong contender. His ability to create countless clones and his massive chakra reserves would give him an edge. Plus, his Sage Mode and later forms are extremely powerful. However, Ging from Hunter x Hunter also has a lot of mystery and power surrounding him. He might be able to outwit Naruto in a battle of wits. But then again, Sasuke with his Rinnegan and Sharingan abilities could also be very formidable in this crossover.
Midoriya and Issei would be an interesting pairing. Midoriya is all about becoming a great hero and Issei is focused on becoming a powerful devil. Their different outlooks and power - seeking goals could lead to some great character development and interactions. Another interesting pair could be Bakugo and Kiba. Both are hot - headed and competitive, so their clashes would be intense and full of energy.
Goku is definitely one of the most popular. His strong sense of justice and his never - ending quest to get stronger make him a great fit to interact with the heroes of My Hero Academia. Another popular one is Vegeta. His prideful and somewhat abrasive personality would create interesting dynamics when dealing with characters like Bakugo. And of course, Deku is also a popular choice as he is the main character of My Hero Academia. Fans like to see how he would react to the overpowered Dragon Ball characters.
I think Deadpool and Eraserhead would be fascinating. Eraserhead's calm and collected nature in contrast to Deadpool's wild and unpredictable behavior. They could have some really interesting conversations, especially when Deadpool tries to get Eraserhead to break his stoic facade.
One interesting pairing could be All Might and Captain America. They both represent the ideals of heroism in their respective universes. All Might, with his One For All power, and Captain America, with his super - soldier serum - enhanced abilities, could have great discussions about the responsibilities that come with their powers. They could also train together, sharing their unique combat techniques.