They aren’t related other than being released on the same day. They are tonal opposites so people are having fun combining them as an unusual double feature.
Admittedly, I’m going to watch one on saturday and the other on sunday because I don’t really want to spend 5 hours at the theater in one day.
"It’s such a tonal handbrake turn that you’ll end up with whiplash, even when Barbie reveals its slightly darker true intentions after about 20 minutes"