Thanks for the excellent guide! I used the wiggle trick to bypass the gate leading to the ??? items in the Debug World (had difficulties getting to that chest with the card, I'm a terrible jumper). Ended up using the wiggle trick to get to that chest, too (wiggled up to the blue "wall" on the east side of the room, and managed to jump to the chest). That wiggling sure is great, also used it to get the 49th card, and to randomly take shortcuts. On a side note...I got the jump shoes from the girl when she met me in the mountains. I just now went back and gave the merchant the box. He was going to give me a card for it (I got excited thinking "but there's not supposed to be a 50th?!?" Turns out, he "lost" the card and healed me instead).
Just out of curiosity, what was the logic behind the solution to the second (hidden) colored block puzzle? Is there any sort of in-game hint that points to that particular arrangement?
Yes, in the blue forest area, north of the temple, there is a grid-like area with coordinates on certain screens. A rock sign tells you there is a secret on (5,3), which turns out to be a cruel joke. However, on some screens there are letters, namely G B and R. These letters and their corresponding coordinates are the hint to the puzzle. The last block's (purple) placement required trial and error, but it only took a few seconds to find it, once the other 3 were correctly placed.