Poor poor Mickey Smith. He loved Rose so much but was stuck in his rut.
When he first was invited into the TARDIS he was too afraid and stayed behind. Even tracking down Margaret the Slitheen was too much for him to handle.
He realizes long before Rose that she is in love with the Doctor and stays behind to protect his grandmother.
Mickey then transforms into a defender of the Earth, jumping across voids to save the planet and even meets someone special