"Mario the Really Useful Engine":
Here's another idea I've come up with, inspired by a popular Sonic 1 hack called "Sonic the Very Useful Engine" by VadaPega. Whenever you collect even a single coin, the music will turn into a full, 16-Bit rendition of the Thomas theme in SMW's instruments, similar to the Sonic hack. Also, when riding Yoshi (who would be redone to look like a tank locomotive), the drums should be replaced with a "chuffing" sound. And the Koopalings could become engines, with Bowser becoming Sir Topham Hatt (The Fat Controller), who replaced Dr. Robotnik in the Sonic hack.
And after accessing the Special World, Mario's face turns Grey, with big eyes and a small, rounded nose, and he gains a "funnel" coming out of his hat. The same thing should happen to Luigi, so you wouldn't have to be Mario to get it to work.

Here's another idea I've come up with, inspired by a popular Sonic 1 hack called "Sonic the Very Useful Engine" by VadaPega. Whenever you collect even a single coin, the music will turn into a full, 16-Bit rendition of the Thomas theme in SMW's instruments, similar to the Sonic hack. Also, when riding Yoshi (who would be redone to look like a tank locomotive), the drums should be replaced with a "chuffing" sound. And the Koopalings could become engines, with Bowser becoming Sir Topham Hatt (The Fat Controller), who replaced Dr. Robotnik in the Sonic hack.
And after accessing the Special World, Mario's face turns Grey, with big eyes and a small, rounded nose, and he gains a "funnel" coming out of his hat. The same thing should happen to Luigi, so you wouldn't have to be Mario to get it to work.
