Yoshi’s Island DS (which was initially referred to as Yoshi’s Island 2) was originally going to be compatible with Nintendo Wi-Fi. Also, one early screenshot showcasing a battle with Big Guy the Stilted seems to suggest that Big Guy was once going to be organic, as he had no patches on him in that picture (although one patch was visible near his right foot, which may merely mean his graphics were slightly incomplete). Finally, one screenshot of an unknown origin shows a Black Yoshi traversing a flowery area with Baby Peach. The particular event illustrated in the picture doesn’t seem to be left in the final game. Baby Peach’s cry was also going to sound more adult- like. [Info from Mariowiki]
Hiccup noticed more differences in the beta videos below:
Different Colour Yoshi’s Maybe?
Big Guy is red like normal shy guys
Classic sound for baby getting on Yoshi
Jumping on bouncy spring Yoshi does different noise
Different jumping Yoshi voices
Quicker egg swallowing?
Pop noise for egg?
Different sound for talking block?
Different sound for red steps appearing?
Different sound for turn pink wheel platform?
Car horn sound for stork stop
Different sound for baby peach crying
Yoshi cant stomp shy guys
Pipe leading up in underground area instead of hole
Different sound for going through middle ring
Different sound for defeating puritan plant
Different enemy, talking block, and flower placement
Completely different end level jingle
Different noise for counting up score
Different Level name display
Different level beginning drums
Different Placement of arrow at beginning with giant tap
World 1-8 Gilbert The Gooneys Castle (final version) has a different the over music (probably because they haven’t finished the music so every level has the same)
The boss of that level has over music too
3D coins and different Yoshi voices (jumping on bouncy jump board)
Also Kieranmay noticed some more differences in the beta:
when yoshi’s got hurt with baby peach on his back, her cry was different like a childs voice
when you swap babies there is a siren which is not in the final version
at the end the music is different when you reach the goal and then when the score is shown (no music is playing)
right at the start, the bongo music sounds different from the final version
baby wario wasn’t present in
on the title screen the birds eye view of yoshi’s island is just stood still but in the final version it shows you all around each side of the island
And adanfime noticed that on video 4 it is shown that Yoshi can run with Baby Peach, when on the final game, Yoshi can only run with Baby Mario!