is a legitimate word and can be found in the bigger desk dictionaries. [...]
John is bigger than Mary, therefore Mary is littler than John.
And in many cases, those patients are littler than you might think!
The dog is little. The puppy is littler. The flea is littlest.
Adjectives and Inflectional Endings Adjective Comparative –er Superlative –est
cool cooler than the coolest
mad madder than the maddest
lean leaner than the leanest
happy happier than the happiest
little littler than the littlest
The World's Littlest Skyscraper | Oddly Historical
The Littlest Rebel is a 1935 American dramatic film directed by David Butler.
“Be a good boy, Oliver,” she said, and handed me to the littlest human. We all walked outside and away from the Kind Lady's house.