bright-eyed and bushy-tailed

3. bright-eyed and bushy-tailed, alertly eager; full of energy and enthusiasm: Get a good night’s sleep so you’ll be bright-eyed and bushy-tailed in the morning.

Eager and alert, as in Here is my new kindergarten class, all bright-eyed and bushy-tailed. The allusion here is to the appearance of a squirrel, which with its beady eyes and bushy tail looks ready for anything. [1930s]