It might be Grandmama from the Addams family. She's a bit of a character herself and has a lot of knowledge about the strange and supernatural. When she meets the Munsters, she might recognize their similar interests and start a friendly chat with Lily Munster about things like potion - making or how to take care of a werewolf.
Probably Gomez Addams. He's always so friendly and enthusiastic. He would likely be intrigued by the Munsters' unique appearance and lifestyle, and would be the first to extend a warm welcome and start a conversation.
Well, it could be a really wild encounter. Maybe Herman Munster and Gomez Addams would start comparing their spooky mansions. They might compete over who has the creepiest decor or the most interesting family secrets. The two families' kids could also get into some strange adventures together, like exploring a haunted forest that's near both of their homes.
Doctor Strange and Ajak. Doctor Strange is well - versed in the mystic arts and Ajak has a lot of knowledge about the Eternals' history and their connection to the Celestials. Their knowledge areas could intersect, and they would likely be the first to start sharing information. Maybe Strange senses some strange energy related to the Eternals and approaches Ajak to find out more.
I think it would be Spider - Man. Since he's also relatively young and has a sense of humor. He would be able to relate to Robin on a more personal level compared to the other Avengers. They could start chatting about their cool gadgets and how to use them in different situations.
Thanos is a likely one. Given their both having grand ambitions in the Marvel universe. In fanfiction, their meeting could be a battle of wills as they both want to be the dominant force. Loki might initially try to deceive Thanos, but Thanos is no fool and would see through Loki's tricks.
Wednesday Addams might be the one to befriend Harry. They both have a sense of being outsiders in their own ways. Harry is an orphan with a strange destiny in the wizarding world, and Wednesday is different from the norm in her family's spooky world. They could bond over their shared experiences of not quite fitting in. Wednesday's intelligence and Harry's resourcefulness could also make them a good pair, sharing secrets and helping each other out in the complex world of Hogwarts and the Addams family affairs.
Iron Man and Batman might be the most likely to clash. Iron Man is all about high - tech and showing off his latest inventions. Batman, while also using technology, is more of a brooding, solitary figure. Iron Man might see Batman as a bit of a relic or too old - fashioned in his methods. Batman, in turn, could view Iron Man as a bit too flashy and irresponsible with his power. Their egos could get in the way of them working together initially.
I think Tooth Fairy would be the first. She is very kind - hearted and is always interested in new things. Elsa's unique ice powers and her beautiful ice creations would draw Tooth Fairy's attention, and she would be eager to make friends with Elsa.
Morticia Addams could also be very interesting. Her elegance and grace combined with her love for all things dark and Gothic would put her in an interesting position with Hannibal. She has a certain allure and mystery about her, and her relationship with Gomez is a study in passion. How she would react to Hannibal's more sinister side, and how he would view her beauty and charm in the context of his own warped world, would be fascinating to explore.
Well, it could be Twilight Sparkle and Spongebob. Twilight is the intelligent and studious one in My Little Pony. She would be intrigued by Spongebob, who is clearly a very different kind of creature from Equestria. Spongebob, on the other hand, would be in awe of Twilight's magic and knowledge. Their first meeting might happen when Spongebob is exploring the library in Ponyville that Twilight often frequents. She would start asking him questions about where he came from and what his world is like.
Probably Percy Jackson from 'Heroes of Olympus' and Magnus Chase. Percy is like the main hero in his series and Magnus is the main character in his. It makes sense that they would be the first to cross paths, maybe because of some strange magical event that throws them together.