Things you didn't notice before in Mario games

I didn't think that SNES Rainbow Road, the shortest Rainbow Road with no railings, was followed by the longest Rainbow Road with railings on the entire track.

I didn't know that SNES Donut Plains 3 and SNES Rainbow Road had a very similar layout.

In 3D World, Rosalina's earrings turn red or bronze when in Fire form.
 
Look carefully at the airship Bowser uses during the opening sequence in Super Mario Galaxy.

You can hit Bowser Jr. with a Star Bit during his boss fight in Super Mario Galaxy. It knocks him over and generates a bunch of Star Bits

It is entirely possible (though not very practical) to defeat Giant Bowser in New Super Mario Bros U by throwing Bowser Jr. at him.

https://www.youtube.com/watch?v=hIVMJC-6Opg

If you look closely at Bowser's renders and Bowser Jr./the Koopalings' renders, you can see that Bowser's skin is scaly compared to the kids who have smooth skin.
 
If you hit the ferris wheel in Water Park, you can hear Toads yelling inside.

The positions of the grounded and aerial boosters at the start of N64 Rainbow Road changes for each race.

You can swim faster on the surface of the water in DK64 by holding B.

If DK and Rosalina stand next to each other in the "No Contest" screen in Smash 4, you can see that DK is taller than her.
 
It took me way too long to notice that the folks in Flipside have square noses and the folks in Flopside have pointy noses.
 
The music in Wii Bowser's Castle is Maple Treeway slowed down.

The music that plays during Peach's Final Smash is a sped up version of the music in the World 9 Warp Zone of Super Mario Bros. 3

In MK8's version of Cheese Land, you can hear your character's voice clips echo when entering the Chain Chomp area.

In the "No Contest" screen in SSB4, you can see that C. Falcon is taller than Rosalina.
 
ThatGuy62 said:
If you look closely at Bowser's renders and Bowser Jr./the Koopalings' renders, you can see that Bowser's skin is scaly compared to the kids who have smooth skin.
Click to expand...
In artwork for Mario Kart 8, but not in artwork for SSB4, the Koopalings too have scales on the yellow skin but not on the green part of the head, while Bowser has visible scales on the green part of the head and different, less visible scales on the rest of the body. Unfortunately, since a Mario Kart 8 Deluxe artwork of Bowser Jr. wasn't made, we don't know if he would have looked like Bowser or like the Koopalings.