I think the Rhino would be a good choice. He's big and strong and could be used as a brute force villain who is hired by some other mastermind to disrupt Spiderman and Megan's life. And Mysterio is also a great option. His illusions could make Spiderman doubt his own senses and even make Megan question if Spiderman is really who he says he is. This would create a lot of tension in their relationship, especially in their newly married state.
Venom would be an interesting addition. Since Venom has a personal vendetta against Spiderman, he could see Spiderman's new married life as a weakness to exploit. His symbiotic nature could make him a very menacing foe. Also, Electro could be in it. His ability to control electricity could cause problems for the couple, like when they are trying to have a romantic dinner and Electro shuts down the power in the city, or he could target the power sources in their home as a way to get to Spiderman.
One possible plot could be that they meet in a rather unexpected situation. Maybe Megan Morse is a scientist working on some project related to Spider - man's powers. As they work together to solve a city - wide threat, they start to develop feelings for each other. Eventually, they get married in a small, private ceremony attended by their closest friends and family. Their married life could involve Spiderman still protecting the city while Megan uses her scientific knowledge to support him from behind the scenes.
Well, if they got married in fanfiction, it might start with an unusual encounter. Perhaps Megan Morzz is initially an adversary, but then they discover they have more in common than they thought. Their marriage could bring together two different worlds. For example, Spiderman's world of street - level heroics and Megan Morzz's world (whatever that may be in the fanfiction). It would be a story of love defying odds and two individuals learning to live with each other's quirks while also saving the city.
Definitely Toad. Toad has been a loyal friend to both Mario and Peach. He could be the one helping with all the little details of the wedding, like arranging the flowers or setting up the chairs. Yoshi could also be a great addition. He could carry Mario and Peach on their honeymoon as a fun way of transportation. Luigi should be there too, as Mario's brother, he would be an important part of the celebration.
Quinn would be an important character to include. Given her past relationship with Puck, her presence at the wedding could add some drama and tension. Santana could also be part of it. She could be the sassy friend who makes sarcastic comments about the wedding but deep down is happy for them. And of course, Mr. Schue. He could give a heartfelt speech at their wedding about how far they've come.
The Joker is always a classic choice. His chaotic and unpredictable nature would create a great contrast to Damian's more disciplined upbringing. It could also put a strain on the relationship between Batman and Damian as they deal with the Joker's madness in different ways.
Lex Luthor would be a great villain. He could see Power Girl as a new threat or an opportunity to manipulate Superman through her. His devious plans and high - tech gadgets would add a lot of drama to the story.
Definitely Mary Jane. She could be in a dangerous situation that forces Spider - Man and Venom to work together. Her relationship with Spider - Man adds an emotional depth to the story.
Cheetah would be a great villain to include. Her connection to Wonder Woman's world and her fierce fighting skills would make for some exciting battles. Also, Bane could be interesting. His brute strength and strategic mind could pose a real challenge to Batman and Wonder Woman when they team up. Lex Luthor is another option. His intelligence and vast resources could create a complex and dangerous situation for the two heroes.
Stefan could also be a character in it. He has a history with both Klaus and Caroline. His moral compass might clash with Klaus' actions at times, which could lead to some interesting conflicts. And his relationship with Caroline as a former love interest could add an extra layer of drama to the married life of Klaus and Caroline.
Inuzuka Hana should be in the fanfiction. As Tsume's daughter, she would play a crucial role in the family dynamics. She might have mixed feelings about Naruto becoming her step - father. Also, Jiraiya would be an interesting character to include. His wild and carefree nature could contrast with Tsume's more serious and stoic personality. He could give Naruto some rather unorthodox advice about marriage, which could lead to some comical situations. And Gaara could be added too. His friendship with Naruto could be shown in the context of Naruto's new married life, perhaps with Gaara coming to visit Konoha and interacting with Tsume.