Nano Banana is a stylized AI image model in Google's Gemini family, tuned for character-consistent illustration. Unlike photorealistic models, it keeps the same illustrated identity — hair, eyes, outfit, proportions, and art style — across many generations when you lock the description. This guide covers the one method that makes that work, the exact-color qualifier trick, and four copy-paste prompt groups for avatars, stickers, logos, and reference sheets.
What is Nano Banana (and what it is not)
Nano Banana is a stylized illustration model in Google's Gemini lineup. It is not a photorealistic model, not a video model, and not a photo editor. It is the model to pick when you need the same character to look like themselves across many images — avatars, mascots, sticker packs, webtoon casts, reference sheets. For photorealism use Seedream 4.0; for editing an uploaded photo use GPT Image 2.
The one rule: a locked character block
Consistency starts with a canonical identity block that you copy verbatim into every prompt. Hair, eyes, proportions, outfit, line treatment, and palette stay fixed; only pose, expression, action, and environment change. Never paraphrase the locked block between generations — if image four drifts, return to the last successful block and change only the scene instruction.
Character Kira: short silver hair, not blonde; amber eyes, not brown; athletic build; white oversized hoodie, dark jeans, white sneakers. Clean illustration, thick black outlines, vibrant limited palette.
Same locked character Kira: short silver hair, amber eyes, white oversized hoodie. Three-quarter profile, slight smile, circular avatar composition. Keep all features identical.
Same locked character Kira. Add a red winter scarf and small snowflakes while keeping the hairstyle, eyes, face, hoodie, proportions, and style unchanged.
Why exact color qualifiers matter
Nano Banana can drift if color words are ambiguous. "Silver hair" alone may generate platinum blonde. Lock the interpretation with a negative qualifier: "silver hair, not blonde", "amber eyes, not brown". This is the single highest-leverage trick for series stability.
- "short silver hair, not blonde" — locks the exact hue
- "amber eyes, not brown" — prevents warm-drift
- "white oversized hoodie" — specify the garment, not just "hoodie"
- "clean illustration, thick black outlines" — lock the rendering style
The prompt formula
Every prompt in a series follows the same shape: [Locked identity] + [Default outfit] + [Art style] + [Current action] + [Scene] + [Composition]. Change only one layer at a time. Keep one style family per series — mixing vector, painterly, and photographic language is the most common cause of drift.
Prompt group 1 — Avatar identity
Character Kira: short silver hair, not blonde; amber eyes, not brown; white oversized hoodie. Clean vector illustration, thick outlines, vibrant limited palette. Front-facing avatar, confident expression.
Same locked character Kira. Close-up portrait, direct eye contact, slight smile. Keep exact appearance, outfit, proportions, and style.
Prompt group 2 — Sticker pack
Same chibi character: round face, short blue hair, red hoodie. Laughing with eyes closed, both hands raised, star sparkles. White sticker outline, transparent background.
Same chibi character: round face, short blue hair, red hoodie. Sitting at a laptop with coffee, focused expression. Keep proportions and palette identical.
Create six expressions of the same chibi character: happy, sad, angry, surprised, sleepy, and excited. Consistent face, hairstyle, clothing, outline, and scale.
Prompt group 3 — Logo & mascot
Brand mascot: friendly round bear, warm brown fur, cream muzzle, green apron, small chef hat. Clean commercial illustration, waving pose.
Logo mark: geometric hummingbird, limited teal-and-cream palette, flat vector, thick outline, centered on white, scalable mascot logo.
Prompt group 4 — Reference sheet
Character reference sheet for Kira. Show front, three-quarter, side, and back views. Keep silver hair, amber eyes, white hoodie, proportions, and line style identical.
Same locked character Kira sitting beside a cafe window, holding coffee, thoughtful expression. Warm afternoon light, clean line art, vertical webtoon panel.
Diagnosing drift
- Hair or eye color changes → broad color words or paraphrased identity text; restore the exact locked phrase
- Clothing changes between scenes → outfit described after the variable scene; move it into the locked block
- Body proportions drift → conflicting style or camera terms; keep one style family and repeat the build descriptor
- Art style becomes inconsistent → mixing vector, anime, painterly terms; lock one rendering style, one line treatment, one palette
Aspect ratios that work
- 1:1 — avatars, stickers, social squares
- 2:3 — portraits and headshots
- 3:2 — multi-angle reference sheets
- 9:16 — webtoon panels and mobile story frames
- 16:9 — campaign banners with copy space
When not to use Nano Banana
- Photorealistic product or portrait photography → Seedream 4.0
- Editing an uploaded photo in detail → GPT Image 2
- Background removal from a real photo → GPT Image 2
- Video or GIF output → no model in our lineup does this; generate stills and animate externally