In the original movie, when Ducky first appears, they exchange these lines.
LITTLEFOOT
Umm...you wanna go with me?
DUCKY
Yeah!...oh...Oh, yes yes yes, I do, I do!
I am presuming that the actress playing Ducky (Judith Barsi, RIP

) may have messed up her line in this scene. My guess was that the original script had the line written simply as:
DUCKY
Oh, yes yes yes, I do, I do!
Now, if that line
was messed up, I believe whoever was in the room at the time thought the screw-up was perfect, considering how cute Barsi was, and with good ideas ahead of them, they must've decided to leave the possible mistake in the recording, with it being animated to later.
Your thoughts on this theory?