ggplot: Global data vs Local data

library(tidyverse)
library(palmerpenguins)
data(penguins)
names(penguins)

## [1] "species"           "island"            "bill_length_mm"   
## [4] "bill_depth_mm"     "flipper_length_mm" "body_mass_g"      
## [7] "sex"               "year"

ggplot(data = penguins) +
  geom_point(mapping = aes(x = flipper_length_mm, y = body_mass_g)) +
  geom_smooth(mapping = aes(x = flipper_length_mm, y = body_mass_g))

ggplot(data = penguins, mapping = aes(x = flipper_length_mm, y = body_mass_g)) +
  geom_point() +
  geom_smooth()

ggplot(data = penguins, mapping = aes(x = flipper_length_mm, y = body_mass_g)) +
  geom_point(mapping = aes(color = species)) +
  geom_smooth(
    data = filter(penguins, species == "Gentoo"),
    se = FALSE
  )