library(tidyverse)

example_df <- tribble(
  ~animal, ~color,
  "Beetle", "black",
  "Lizard", "purple"
)

example_df_lower <- example_df %>% 
  mutate(across(where(is.character, tolower)))
#> Error in `mutate()`:
#> ! Problem while computing `..1 = across(where(is.character, tolower))`.
#> Caused by error in `across()`:
#> ! unused argument (tolower)

library(tidyverse)

mtcars|>
  ggplot(aes(x = mpg, y = cyl)) +
  geom_point(aes(shape = 12), color = "purple") 
#> Error in `scale_f()`:
#> ! A continuous variable can not be mapped to shape