SET-UP:
You may not even notice them at first, but kill 5 snails on your crusades. After killing 5 different snails, you will need all 5 outer locations unlocked. (Lonely shack, Pilgrim's passages, Spore grotto, Smugglers sanctuary, and Midas' cave.)

GETTING THE FOLLOWER FORM:
Find a snail statue in each one of the maps, you must give them a snail shell from one of the snails you killed. They will be hidden. Here is were all of them are;
Lonely shack: behind the shrine
Pilgrims passage: to the left of the lighthouse
Mushroom grotto: on the left side of Sozo's room
Smugglers sanctuary: next to the crates on the left side
Midas' cave: go to the center area, then head to the bottom right corner of that area.

And boom, the snail follower form!

Thank you for reading, so while your at it, Midas' cave has a starfish/Midas follower form behind one of the front gold piles!