Carver wasn't sick
Somehow he found out about the plot, or at least figured out either that he'd be stealing from the guy whose wife he recently killed, or about the presence of the other assassins, and faked being sick so as to not have to take the risk. Far fetched? Maybe. But the W of WMG does stand for wild.Specifically, he's Wade Wilson before he becomes Deadpool. The organization he and Ladybug work for in the film could easily be his main work, with the Sister Margaret's gig simply being a side job for quick cash. And like Ladybug, Carver is just a codename assigned to him by the organization.Also, playing off the above WMG, Wade WASN'T lying about being sick. He'd just gotten his cancer diagnosis, and was dealing with that during the events of the film.
The film takes place in the same universe as John Wick.
The criminal underworld of White Death could very easily take place in the same world. Not only that, both films feature the novel Shibumi by Trevanian (the security guard that let's John onto the airport runway in the first film was reading the book, The Prince is seen reading it during the first half of the film).- By this logic, does this mean that The Elder is Shimazu? If so, his daughter turned out way better than his son did.
- This WMG was posted back before John Wick: Chapter 4 came out. However, it could be possible to explain that the Elder is Shimazu and was running The Continental Osaka when the events of Bullet Train occurred. The Father being the way he is while Akira is bad-ass is because The Father had a kid and Shimazu wanted to keep him away from the crime world (but due to the Prince, he got dragged into it when she harmed his kid and tried to use his history as a cover for her assassination plan. And she probably chose him because unlike Akira, he would be easier to manipulate because The Elder wasn't around him as he was around Akira). This would explain how the Elder had someone watching over his grandson (as the woman is a staff member of The Continental Osaka). A little Canon Welding can make it fit.
Ladybug, Carver and Maria work for the International Contract Agency
If a follow-up film is ever made...
If a follow-up film is ever made for this one, Carver will turn up and will end up being killed in the most brutal way due to his part in causing Ladybug grief.The nurse protecting Wataru in the hospital is a surviving family member of the Minegishi organization, possibly even Minegishi's daughter.
The nurse doesn't appear to be much older than Yuichi (her actress, Charlene Lee, is 9 years older than Andrew Koji, who plays Yuichi) putting her right around mid-teens when the White Death took over the organization by killing Minegishi and all his supporters. While it is possible that The Elder still has connections in Japan's criminal underworld, it makes more sense that he would have sought out other survivors of the White Death's purge to gather allies for his attempt at revenge. He went to get on the train before he knew the White Death would be at Kyoto Station, explaining why he didn't bring these other allies along.Lemon and Tangerine are a result of superfecundation
Whilst the two of them being biological twins but completely different races was likely done as an ironic twist of the original reason why they're known as "the twins" (in the book, they're identical but aren't blood related), it is actually possible in real life. Superfecundation is the process where two or more ova are fertilised by different fathers, allowing for twins to be born of different races. If Lemon and Tangerine are the result of this, then it might suggest that their mother was a sex worker of some description, or that one of the two are the result of an affair.Ladybug only thinks he's a thief. His organization actually uses him as a Walking Disaster Area for other criminal organizations.
Ladybug's terrible luck, refusal to use his considerable combat skill for anything other than defense, and frustrating personality are reasons in and of themselves to fire him... unless those are exactly the reasons he gets employment. Whenever the organization he works for wants a group of assassins or specific crime boss dead, they send him in on a seemingly simple job knowing that the chaos his mere presence causes will wipe out all those threats in one fell swoop. The trick is, he's the only one who doesn't know this. Considering he reflects on previous "simple" jobs that resulted in massive bloodbaths for otherwise formidable criminal organizations, it's implied that the chaotic events on the train are just sort of what happens when you send Ladybug anywhere.Ladybug's true identity is Jerry Welbach from The Mexican.
Both are habitually unlucky and yet have a knack for getting out of trouble relatively intact. Both are primarily couriers for the criminal underworld. And, both are very similar in personality, with Ladybug being a little more mature, which would make sense as he'd have many more years of life experience.