Starscream and Pinkie Pie could be an interesting combination. Starscream is always plotting and scheming, while Pinkie Pie is full of randomness and joy. Their interactions would be hilarious. Maybe Pinkie Pie's positive attitude could even start to change Starscream's devious ways, or at least drive him crazy with her unpredictable behavior.
Megatron and Darth Vader could be a very dark and powerful pairing. Both are iconic villains. Megatron's thirst for power over Cybertron and Vader's loyalty to the Emperor are similar in nature. They could form an alliance, plotting to take over both the Cybertronian and Star Wars worlds. Their combined might would be a huge threat to the heroes, and it would be interesting to see how the Autobots and the Jedi would counter them.
Optimus Prime and Thor would be a really interesting pairing. They are both noble leaders. Optimus with his wisdom and strength, and Thor with his godly powers. They could exchange ideas about leadership and honor while fighting side by side against powerful foes. Their weapons are also quite interesting to compare - Optimus' ion blaster and Thor's hammer.
One idea could be that the Autobots find themselves in Equestria due to a space - time rift. They team up with the ponies to fight a common enemy like a new breed of Decepticons who are after the magical energy in Equestria. The ponies could use their magic to help the Autobots repair and upgrade, while the Autobots offer their advanced technology to protect Equestria.
Popular characters in Transformers Prime: Darkness Rising fanfiction are often Optimus Prime due to his leadership and moral compass. He's the hero that many stories revolve around. Bumblebee is also highly popular as he represents the connection between the Autobots and humans. His ability to communicate through radio and his loyalty are endearing traits. Megatron is another key character. His tyrannical rule and his thirst for power over the AllSpark make him a great villain. Arcee, with her combat skills and her own backstory, can also be an interesting character to include in fanfiction.
Arcee from Transformers Prime can be an interesting character to include. Her agility and combat skills can be a valuable asset in the Beast Wars battles. For Beast Wars, Rattrap is a fan - favorite. His sarcastic humor and street - smart nature can add a touch of lightness to a story that might otherwise be full of intense battles. Also, Ratchet from Transformers Prime could be in a fanfiction where he has to deal with the different medical needs of the Beast Wars characters, which could lead to some really engaging storylines.
Ash Ketchum from Pokemon is a common character in these crossovers. He's a Pokemon trainer, and in a crossover, he could come to the world of MLP and start showing the ponies about Pokemon training. On the MLP side, Rainbow Dash is popular. Her adventurous and competitive spirit would make her eager to try out Pokemon battles or learn about different Pokemon species. So, a story with Ash and Rainbow Dash could be full of action and excitement.
Obviously Discord himself is a very popular character to feature. His chaotic nature and powerful magic make for interesting storylines. Pinkie Pie is also a common choice as her zany personality can either clash or complement Discord's chaos in really fun ways.
Definitely Master Chief. His stoic nature and combat skills would be really interesting to pair with Pokemon. He could be a silent but effective Pokemon trainer. Another would be Cortana. Her intelligence could be used to analyze Pokemon abilities and strategies. And of course, Pikachu would be a great character to include. It could be fun to see how it interacts with the Halo characters and technology.
Zane would be a great character to include. He has his own charm and knowledge of the human world. If he were in a crossover, he could introduce new technology or ideas to the other mermaids. For example, if he crossed over with mermaids who are more primitive in their ways, he could help them modernize their defenses against threats. And he could also learn a lot from their ancient magic and traditions.
Mewtwo could be a very interesting character in this crossover. Mewtwo is a powerful and intelligent Pokémon. In a fanfiction, it could be intrigued by Ben's Omnitrix and the concept of being able to transform into different beings. Mewtwo might initially see Ben as a threat or a potential ally in its own quest for power or understanding of the world. This could lead to some intense and thought - provoking interactions between Mewtwo and Ben.