When Petunia says "beach", she makes the sign for "peach". I guess the words sound the same to her, and none of us know the sign for beach.
And I love how both of my kids say "thank you" right now, as demonstrated in the following recent conversation:
Pumpkin, to Petunia, after agreeing to turn off her show so that Petunia could watch the show she wanted: Say stank you, Petunia, say stank you.
Petunia: Gank oo.