While viewing the Daisy trophy, some clever camera changes will get you "between" Daisy's hair and the back of her head, revealing another eye behind her right ear! Finding it can be a bit tricky on your own; the following directions will get you a good view of the eye using the least amount of motions.

Move the C-Stick left or right to rotate the trophy so that you're looking at the back of it.
Hold the Y button to zoom in as close as you can.
Using Down on the Directional Pad, move the camera up until you see the bottom of Daisy's crown.

From there, moving the C-Stick down will let you see through the hair, revealing the eye.
From that position, you can move the C-Stick around to get different angles of the eye.

Freaky! Since the third eye was removed in later versions of SSBM, it was definitely unintentional.