Ensemble Dark Horse: Toad. He's by far the most popular character and tends to get top billing in just about every adaptation there is.
Summed up by later episodes of the Cosgrove Hall TV series devoting the end credits to Toad's song (with the lyrics taken directly from the book).
Ho Yay: Mole and Water Rat show shades of this. Living together is possibly the least intimate gesture that passes between them. Terry Pratchett commented that "the Mole and the Rat's domestic arrangements are probably acceptable, but only if they come out and talk frankly about them."