What do I do with Mystery Mouse on level 46?

Dani_Lynne

On level 46 Mystery Mouse comes out and highlights a certain letter.  What is this for?  And how do I use Mystery Mouse?  It tells me that he can help me, but you don't give any hints or explanations?

StuckInATree

The Mystery Mouse comes along at the start of the game and adds 1 Crown to a tile on the board, it also gives you 5%  score increase! The description of what they do can be found below the characters in the library if you are curious.