Brain Game: In the Past
By BY

Welcome to the Brain Game, a five-days-a-week feature here on www.mentalfloss.com.
By adding one letter at a time (and rearranging the letters as necessary) to form new words, convert the word "I" into the word "ERSTWHILE." Good luck!
I _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ E R S T W H I L E
Here is one SOLUTION.
ONE SOLUTION:
I > IS > SIT > THIS > SHIRT > THEIRS > WITHERS > WHISTLER > ERSTWHILE
Did you come up with a different solution? Please share it with us in the comments. Thanks for playing!