Please generate a sticker sheet containing LINE sticker images arranged in a grid layout (either 2 to 3 columns and 2 to 4 rows), based on the reference character design.

**Character & Art Style:**
- Character: Use the exact same character design from the reference image (a friendly white-and-green robot with headphones and a small green sprout on top).
- Style: Cute, flat vector illustration, colorful, thick white outline around both the character and speech bubbles.

**Grid & Spacing Requirements (Crucial):**
- Layout: 2 to 3 columns and 2 to 4 rows (e.g., 2x3, 3x3, or 3x4 grid).
- Vertical Spacing: Clear, continuous horizontal transparent space between EACH row (no vertical overlap between rows).
- Horizontal Spacing: Clear transparent gaps between individual stickers in each row (stickers do NOT need to align perfectly into vertical columns, as long as there is distinct space between neighboring stickers).
- Background: Transparent background (PNG).

**Sticker Content & Expressions:**
Include common English daily greetings in bold, clean speech bubbles with expressive poses:
1. "Hello!" (Greeting with a wave)
2. "Thank you" (Holding a big heart)
3. "Yay!" (Jumping with joy)
4. "Nice!" (Thumbs up)
5. "OK" (Polite bow with "OK" hand sign)
6. "Good job!" (Fist pump for encouragement)
7. "Good night" (Sleeping peacefully on a cloud)
8. "Peek-a-boo" (Peeking from behind a wall)