Well, perhaps the poker game is a test of loyalty. In this 'Harry Potter fanfic', different houses could be pitted against each other in the poker game. And the winner of the game might get a special magical item that has been lost for centuries. It would be full of strategic plays and magical elements within the game.
One idea could be that the characters play poker to decide who gets to use a powerful magical artifact for a day. For example, Harry, Ron, and Hermione play against the Slytherins.
Harry Potter himself could be one of the main characters. He might be drawn into the poker game by his friends Ron and Hermione, who think it could be a fun way to unwind from their usual magical adventures.
Obviously, Harry Potter himself could be a main character. He might be using his skills of strategy from his adventures to play poker well.
One idea could be that during a Quidditch match, a player gets seriously injured. Instead of using magic to heal right away, an ambulance from the Muggle world is called in by a confused bystander. The ambulance crew has to deal with the magical aspects they've never seen before while trying to transport the patient to a Muggle hospital. This could lead to a lot of comical and also tense situations as they try to figure out how to handle the situation.
One idea could be a wizard discovers Beyblades in the Muggle world and decides to bring them to Hogwarts. He then challenges his classmates to Beyblade battles instead of duels. The different houses could form their own Beyblade teams and compete in a tournament, with the winning house getting extra house points and a special magical Beyblade as a prize.
One possibility could be that Supergirl somehow ends up in the wizarding world of Harry Potter. Maybe she's chasing a powerful magical artifact that has fallen into the wrong hands in Hogwarts. She could use her superpowers to help Harry and his friends during a particularly tough battle against Voldemort, like using her heat vision to fend off Dementors or her super strength to break through some dark magic barriers.
One idea could be Harry using parkour skills to escape from the Death Eaters in the Forbidden Forest. He jumps from tree to tree, slides under fallen logs, and uses his magical abilities in combination with his newfound parkour skills to outmaneuver them.
One idea could be that Voldemort discovers the power of the Stargate and tries to use it to gain more power. He could send his Death Eaters through the Stargate to conquer other worlds and bring back resources or powerful artifacts to help him in his quest to take over the wizarding world. The Order of the Phoenix would then have to follow through the Stargate to stop him.
One unique feature is the use of magic. For instance, the cards could be self - shuffling or have pictures that move. In some fanfictions, the players can use spells during the game to bluff or influence the outcome.
One idea could be that the Justice League somehow ends up in the wizarding world. Maybe a magical portal opens during a battle in their universe and sucks them into Hogwarts. Superman's powers could be affected by the magic there, and Batman would be intrigued by the complex magic system and start studying it. Harry Potter and his friends could team up with the Justice League to fight a new dark force that threatens both the magical and non - magical worlds.