All 15 collectibles - "Collector" achievement

This guide will show you the locations of the 15 collectibles needed to get the "Collector" achievement.

Where to get all 15 collectibles

This guide will quickly show you the locations of all hidden collectibles needed for the "Collector" achievement. You need to get all 15 of them in one playthrough. Activating infinite lives will not prevent you from getting the achievement.

1. Level 1 - Mt. Eternal:
   In a block to the right of one of the stone villagers.
   
   
   
2. Level 3 - Lake Fathom:
   Kill the 2nd octopus.
   
   
   
3. Level 4 - The Island of St. Nurari:
   In a blue block soon after the 2nd lava pit.
   
   
   
4. Level 5 - Namui Lake:
   Lose the helicopter and fall into the water at the start of the level. The collectible will be in a block a bit further.
   
   
   
5. Level 6 - The Village of Namui:
   Talk to the dog and the collectible will appear.
   
   
   
6. Level 7 - Scorching Pathway:
   In a block right above the first circling flame.
   
   
   
7. Level 8 - Mt. Kave:
   In a block under the pink block with a star on it.
   
   
   
8. Level 10 - River:
   Lose the boat and drop into the water. The collectible will be in the bottom line of blocks right before the end of the level.
   
   
   
9. Level 11 - Taiyo Desert:
   Quite early in the level, in a block on the ground between two circling flames.
   
   
   
10. Level 12 - Bingoo Lowland:
    Buy the helicopter in the shop at the start of the level and get past the first two lightning clouds without losing it. The collectible will be right after that, in a line of blocks on the top of the screen.
    
    
    
11. Level 13 - The Radaxian Castle:
    Talk to the first knight you encounter and the collectible will appear.
    
    
    
12. Level 14 - The City of Radaxian:
    In the topmost block above the 2nd circling flame.
    
    
    
13. Level 15 - Toxic Numachi:
    In a block above a pair of green blobs.
    
    
    
14. Level 19 - Janken's Fortress:
    In a block next to a circling flame, before a stone thrower.
    
    
    
15. Level 20 - Janken's Castle:
    During the underwater section, the collectible is directly visible in the spikes room.
    

There you are. You should get the achievement as soon as you pick up the last collectible.
Enjoy your full collection!

[Alexus]

Ty for the guide

[Titler]

"Does anyone know what the 12th one (the rose) represents? Is it from a Sega game or was it from some kind of promotion?"

The Alex Kidd wiki indicates it's a reference to the Bayonetta series.

[Titler]

"It is possible to get without buying heli on stage 12, with some micro jumping"

Regarding this, knock out the upper of the two destructable blocks in the vertical, jump up via the remaining destructable, and above the line of blocks that hide the collectable. Then leap off the end block, turn back left in mid air and punch the block on the end as you drop by. Climb back up and keep repeating until you get to the last one which hides the collectable.

[Titler]

You CAN get the collectable and the secret level on the same game run, but you get the collectable first by killing the second octopus, then exit straight to main menu, then restart the game which puts you at the start of the level again. Now kill the first octopus and go to the secret level.

[frod]

Psycho Werekitsune - It is possible to get without buying heli on stage 12, with some micro jumping

[Galvancito1]

Does anyone know what the 12th one (the rose) represents? Is it from a Sega game or was it from some kind of promotion?

[Psycho Werekitsune]

No, accessing the secret island doesn't allow you to get the SECOND collectible in that very same level since it appears by defeating the second octopus later on in the level.

Also, is there a way to get the collectible in Bingoo Lowland without the helicopter? I'm trying to avoid buying anything from the shop for the achievement.

[LetsPlayNintendoITA]

wait... accessing secret island doesn't allow you to go to the next level and get the 3rd collectible?

[Psycho Werekitsune]

Yeah, I was referring to the latter. Didn't think about losing all my lives, that's not a bad idea.

[kapinou]

Psycho Werekitsune > If you're speaking of getting both the 2nd and 3rd collectibles, just don't go to the secret island and get to the "normal" end of the underwater level. As LetsPlayNintendoITA said, the 3rd collectible is on the next level, "The Island of St. Nurari", not on the secret island.
If you're speaking of both getting the 2nd collectible and accessing the secret island, the only way that I see is to lose all your lives after getting the collectible in order to restart the level, as the collectible will carry over after the game over. There's not much point to this though.