Joke: Gyrados was originally the final evolution of the Dratini line because they are all long and blue.

Broke: Game Freak swapped around Butterfree and Venomoth during development, which is why Butterfree has more similarities to Venonat than Caterpie and vice versa.

Woke: Blastoise was originally completely unrelated to Squirtle and Wartortle, with its own pre-evolution, but was made into the final evolution at some point during development, presumably due to redundancy.