The Wild Thornberrys is often regarded as one of the best Nicktoons of all time, but it's actually really messed up. Sure, the TV show has some great episodes, but Donnie's dark backstory definitely makes us do a double-take. How could this little boy be treated the way he is?
Though none of Nigel and Marianne's children have a normal life (they're busy being homeschooled, traveling the world, and talking to animals), Donnie has a particularly tragic experience. His life has been marked with loss and abandonment. When he's not busy trying to learn the English language on his own (he's picked up a few words despite never being educated), he's struggling to show his adoptive family his unique talents.
Donnie's horrible past is one of the bleakest Thornberry secrets. The adopted feral child is treated like an afterthought and is treated as such the moment his beloved orangutan surrogate mother gives him up. What Nickelodeon never explains is how the Thornberrys get away with their horrid mistreatment, how the village got away with it, and how the poachers who claimed Donnie's parents' life got away with it.