I've just watched the longplay of Super Mario 3D Land, and have some advice for you. I work with casual games for about a year, and those sounds is from my type of work.
The basic rule for this SFX's is "imagine, that everything is tiny". It's like living in a toy world. The sounds is more rounded and all envelopes is as glide as possible. In foley try to use small pieces of wood, stones, plastic and much much more. Keep an eye on "candy", warm sound. Often it appears in rattle sounds. Just cut that small pieces (they can be very short some times). They are hard to get at first, but with some time spend on it, you start to hear them really well. Also you can hear them in big events, the most popular place is in a tale of explosions, cracks, drops and everything else that divides itself in to pieces. Just cut the tale and gain it up. You can hear a whole new world. Yes, the rattling stones on the seashore is welcome too.
Aim for develop your personal library with that tiny sounds. These would be very helpful in future, for interface sounds for example.
For the music pieces (jingles) use pitched percussions (marimba/xylophone/glocken etc.), combine them. They must be as tiny and dotted as possible - with no attack, sustain and release. Just a "pixel of sound". Most of instruments will be very sharp with this settings. To glide them just double the melody on a few instruments and slightly move left/right. Not too far, just to produce more smoothly and little bit of rattling sound. Just like a stones on the seashore. One of the best instruments for that goal is Korg M-1.
On the effects side the plate reverb and phaser will help you round these small pieces. Apply them not too much, just for subtle feeling. It must sound natural and warmy.
I hope my experience will help you!