1. Knee-high to a grasshopper. - Nagyon fiatal, vagy nagyon alacsony emberről beszélünk.

For example: The last time I came here I was knee-high to a grasshopper.

2. I have butterflies in my stomach. - Pillangók vannak a gyomromban. (Nagyon ideges vagyok.)

For example.: I used to have butterflies in my stomach before school tests.

3. To have ants in his pants. - Hangyák vannak a nadrágjában. 

For example: She's got ants in her pantsbecause she's going to a party tonight.