What exceptional words turn into other words by insertion of letters?

language/english/spelling/operations.on.words/insertion

Problem

What exceptional words turn into other words by insertion of letters?

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   longest hydration (double reheadment)  (D,R)EVOLUTIONIST (12/13)
   longest hospitable word (insert letter anywhere) 
    CARES: SCARES, CHARES, CADRES, CARIES, CARETS, CARESS 
   shortest hostile word (no deletion possible)  SYZYGY (6)
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Unless noted otherwise, all words occur in Webster's Third New International
Dictionary, Merriam-Webster, Springfield, MA, 1961.