You start with three clean plates but as you progress and start doing well you will need more so it is important that you have clean plates available. If you don't have clean plates you will end up having fully assembled meals sitting there that cannot be sent out to the hungry customers which will mean you will lose tip points and possibly your tip multiplier. To clean dirty plates you need to take them to the sink and clean them by holding the Chop/Throw button.
<br><table width='100%' cellpadding=3 cellspacing=3 border=0><tr valign='top'><th>Unlockable</th><th>How to unlock
</th></tr><tr valign='top'><td>Kevin 1</td><td>Level 1-3: Achieve a combo of 2 (solo or co-op)
</td></tr><tr valign='top'><td>Kevin 2</td><td>Level 2-2: Achieve a combo of 3 (solo) or 5 (co-op)
</td></tr><tr valign='top'><td>Kevin 3</td><td>Level 2-4: Achieve a score of 600 (solo) or 1,000 (co-op)
</td></tr><tr valign='top'><td>Kevin 4</td><td>Level 3-1: Achieve a score of 450 (solo) or 1,100 (co-op)
</td></tr><tr valign='top'><td>Kevin 5</td><td>Level 4-3: Achieve a combo of 4 (solo) or 5 (co-op)
</td></tr><tr valign='top'><td>Kevin 6</td><td>Level 4-5: Achieve a score of 400 (solo) or 500 (co-op)
</td></tr><tr valign='top'><td>Kevin 7</td><td>Level 5-5: Achieve a combo of 5 (solo) or 8 (co-op)
</td></tr><tr valign='top'><td>Kevin 8</td><td>Level 6-4: Achieve a combo of 5 (solo) or 7 (co-op)
</td></tr></table>