I remember finding the Arthur book where D.W. refuses to eat spinach at a restaurant. It was just like that episode I remember seeing which got me started watching Arthur.
Not quite. I think I either read or had the book... I can't remember if it had the same subplot about going to Grandma's birthday party, but I do know the fairy tale theme wasn't present in the restaurant outside of the kid's menu. But the most prominent change is that D.W. isn't exactly happy at the end of the book when she discovers that she ate spinach. Similar to how the book version of Arthur's Chicken Pox, she wasn't happy to have caught it at the end.
Now, for Teacher Trouble... when they adapted that into an episode, they actually split the story up into 2 parts to make 2 different episodes.... now, the book combines the fact that they get in the rat's class and the spelling bee at the end (this book, actually, I got this one autographed by Marc Brown YEARS before it became popular outside the book series). With the TV show, they added the segment about Buster and Arthur stalking him to find out if he really was evil, and prolonged the spelling be preparations both to fill out episodes.
I'd dare say the only episode that was really close to the book was Arthur's eyes... the only major change being the picture day segment was removed and made its own episode (and appears to take place later in time) and the fact the story was told in flashback form... I think the bit about Bionic Bunny's actor wearing glasses was also added, but I know the teacher had a similar pair. Arthur's Tooth was also kinda close.