It could be that his head wasn't screwed on just right, or it could be, perhaps, that his shoes were too tight.
8 seconds sound clip from the How the Grinch Stole Christmas (2000) movie soundboard.
You can hear this line at 00:06:45 in the Blu-ray version of the movie.
Quote context
[...]
- You see, Max? The city is a dangerous place.
- The Grinch hated Christmas, the whole Christmas season.
- Now, please, don't ask why. No one quite knows the reason.
- But I think that the most likely reason of all may have been that his heart was two sizes too small.
- Hey, stranger, won't let you go till you buy a chapeau!
- The streets are filled with Christmas cheer.
- Boy, nothing beats Christmas, right?
- I guess.
- Well, it's just... I look around at you and Mom and everyone getting all kerbobbled.
[...]