The show's subtitle, Static Cling, has a double meaning to it. Not only does it refer to how Rocko is trying to get Fatheads back on the air (since televisions produce static if they don't have a signal), but it also refers to how those who don't accept change try to cling onto what they're familiar with, like what happens with Ed and Rocko.
Considering their Fatheads tape was the only thing they watch during their exile in space, it explains why Rocko is so obsessed with it in the special.
Biologically, it's possible for certain types of frogs/toads to change between genders based on environment, genetics, and even pesticides (indeed, this was a plot point in Jurassic Park). As a toad, it made sense for Ralph to become Rachel.
Ed being the one to give Rocko the moral lesson shows how much he has learn to accept change. Before, he would have relish anything that would have made Rocko miserable as a victory but he knows that he has to make other changes in his life in order for it to be better so he is changing his relationship with Rocko by encouraging him to embrace change in his life.
Both heartwarming and this is Rocko, Heffer and Filbert's acceptance of Ralph transitioned to Rachel. Their favorite superhero is genderfluid (Really Really Big Man's alter ego is a woman called Lois Lame).
At first, it's slightly confusing that the narrator in the rebooted Fatheads cartoon refers to the baby Fathead with "he/him" pronouns, as the baby is Rachel's Author Avatar and she's a trans womannote most trans people prefer to be retroactively referred to by their current gender, not their assigned gender, and the baby character has a pink bow in their hair. However, this could be why the baby's such an Enfant Terrible — everybody keeps calling her by the wrong gender!
