Can Someone Please Tell Me....

Can someone please tell me why a child who seems to absolutley love a particular food, so much that he eats the entire bowl of it, will two days later, when trying to be fed the same EXACT food again, spits it out, and furrows his eyebrows at his mother. Yeah, happens alot!

Also, could the same someone tell me how to baby proof when your child figures out that he can stand ON A DOG to get on the couch. Came into the living room the other day to find Nick on the couch. I couldn't figure out how in the world he got up on the couch. Until I saw him do it again. Took a photo, then got him down, again. How do you baby proof this?????