To join the ranks of the Straw Hat Pirates, you need to be more than skills. You need to have perseverance, you need passion, and need to be ready to face the deadliest pirates and naval officers the world has ever seen. Most importantly you need to put up with its idiot of a captain, Monkey D. Luffy.
As far as recruitment goes, Luffy is a chill captain that's all about helping his crew achieve their dreams and having a good time. If they got cool flashy powers and aren't a total jerk, he'll want them on his crew in a flash. That being said, he does have a policy against jerks so he won't welcome everyone with open stretchy arms. It also goes without saying that there are those who want nothing to do with Luffy. These are five heroes who'd be Luffy's sidekick and five he'd never work with.
10 Sidekick: Harley Quinn
It never hurts to have a second doctor on the ship unless that doctor is Harleen Quinzel. She was practically destined to become part of the Straw Hat Pirates and its manic crew of misfits. Harley is crazy enough to go along with any plan that Luffy concocts and has no problem picking fights with authority figures or rival gangs. Aside from being a fun shipmate, she's also an incredible acrobat, a trained psychologist, master of disguise, and immune to toxins and poisons. In no time she will oust Buggy as the top clown pirate in the world.
9 Never Work With: Gwenpool
Gwenpool does have similar abilities as Harley but she also has the same abilities as Deadpool. Including the ability to break the fourth wall. Given the series's reputation for excessively long story arcs, Gwenpool would be bored out of her mind. She'd try to rush fights along or make fun of the 4Kids version and no one would understand what she's talking about.
Zoro wouldn't like having a rival swordswoman on the team and the crew would get annoyed with her eventually. This is one crossover that won't happen for all the right reasons.
8 Sidekick: Moon Girl and Devil Dinosaur
Lunella Lafayette AKA Moon Girl alone is more than qualified to join Luffy's crew. Her IQ is off the charts making her one of the smartest beings on Earth and a brilliant inventor that surpasses Usopp. Luffy be blown away by her contraptions and he'd ask her to modify his ship with all sorts of gadgets. But those aren't going to capture his attention initially. Devil Dinosaur is what will get his attention. Luffy would do anything to get a dinosaur on his crew and Lunella would use the opportunity to join a crew that acknowledges her gifts and intelligence. She just needs to make room on the ship and be careful that Luffy and Sanjay don't try and cook her dinosaur
7 Never Work With: Swamp Thing
Swamp Thing is a powerful being with a strong connection to the Green and would make a fine addition to the Straw Hats. The problem is his role as the impartial protector of the environment. He has no interest in reaching the Grand Line or becoming the best at something so Luffy would have nothing to entice him with.
Unless he and Luffy share a common enemy that happens to be endangering the environment, Swamp Thing wouldn't care about the conflict between the World Government and pirates. Not to mention he's a real bummer that would kill the crew's vibe.
6 Sidekick: Static Shock
There are a lot of superheroes in DC that are worth recruiting with many that haven't been in the lime light for sometime. Of course Luffy is an impulsive guy that would likely pick heroes that could amaze him which is why he'd pick Static Shock. On top of possessing electrokinesis, Static also has control over electromagnetism allowing him to fly on his saucer or stick enemies to walls with static cling. Static would be invaluable since he could decimate enemies without hurting Luffy since his rubber body doesn't conduct electricity. The only downside is his electricity is sure to mess up Chopper's fur but Luffy would see that as a perk.
5 Never Work With: Black Bolt
Any crew that had Black Bolt with them would practically be unstoppable. Unfortunately, he wouldn't last a week with Luffy. He could handle any threat that gets tossed at him but he doesn't have the patience to put up with the captain. Always the childish one, Luffy would pester him relentlessly trying to get him to talk once he learns of the power of Bolt's voice. Luffy would wait until they were in an open field or sailing on the open ocean but he wouldn't let up until Black Bolt spoke. At best, he would only get two words out of the king: I quit.
4 Sidekick: Ms. Marvel
Kamala Khan is just what Luffy looks for in a shipmate. Bright-eyed, idealistic, has big dreams, and incredible powers. Carol Danvers is a fine idol, but Luffy could teach her a thing or two about her shape-shifting powers since it's similar to his Gum-Gum powers.
As unlikely as it is to think of Luffy as anyone's teacher, he'd at least want to show off and have fun training with someone who has similar abilities. Kamala would at least admire Luffy's selflessness and know that though they're pirates they are doing good. Luffy may not be the ideal teacher but she would be the ideal sidekick.
3 Never Work With: Mr. Fantastic
Reed Richards might be the smartest man in the room but that doesn't mean he's the most liked. He's stubborn, prideful, and unlikely to follow any of Luffy's orders. If it's anything like when he briefly joined the Avengers, he'll be bickering with Luffy over their next plan and try to take control. He'd also likely study every member of the crew who's eaten a Devil Fruit and get on their nerves. On top of all that, Reed lacks the charisma Johnny has and would be kind of a buzzkill to have around. Maybe it's best that he sticks with the Fantastic Four and stay there.
2 Sidekick: Shazam
While Luffy may have the heart of the child, Shazam is an actual child. One that would be living every child's fantasy of being a pirate, sailing the seas, and hunting for treasure. As for Luffy, he would do anything to get a crew mate that has super-speed, super-strength, and is practically immortal. Plus most of the crew is generally good with handling kids and would act as a family to the Billy Batson. Though knowing Luffy, he'd probably recruit Billy Batson and Shazam and never realize they're the same person until months later.
1 Never Work With: Aquaman
On paper, Aquaman would be the ideal crew mate considering Luffy and his crew spend most of their time out on the open ocean. That is until you consider the fact that Aquaman isn't fond of pirates. The Straw Hat Pirates aren't as bad as other pirates but it would make it difficult to work together. Especially since Sanjay's goal is to reach the Deep Blue and cook up rare, exotic fish that might be endangered. Luffy would have better luck casting his net somewhere else.
