MoreThanBored, fellow Cave-Story fan, you get a Machop named Quote.
In the beginning of Cave Story, Quote has amnesia, and can only use the Polar Star.
Similarly, your Machop can only use the attacks he knows when you catch him. (He can learn others, he just can't use them)
However, as he progresses through the game, he learns to use other attacks, just as Quote learns to use other weapons.
When you get your second gym badge, Quote finds the Missile Launcher and can use one new move.
When you get your third gym badge, Quote receives the Fireball and can use one new move.
When you get your fifth gym badge, Quote receives the Blade from King, and can use one new move.
Finally, when you get your seventh gym badge, Quote receives the Super Missile Launcher after defeating Balrog (My avatar can beat up your avatar) and can use one new move.
At any time, you can go on a side-quest and exchange one of your current moves for a TM/HM.
You must solo three trainers in a row without fainting, visiting a Pokémon center, or using healing items.
After that, you can learn a single TM or HM OR evolve.
Quote cannot learn a TM/HM or evolve without completing a new side-quest.
To prove himself, rescue Curly, complete a very lengthy chain of sidequests, and save the day, Quote must solo one gym leader and at least three Pokémon in the elite four.