Related Clues:

• Irregular in habit or movement
• Liable to sudden unpredictable change
• Unpredictable, temperamental
• Liable to change rapidly and unpredictably
• Little by little he is about to be a pest, but not a regular one
• Not even this will do wrong with a twitch
• Not the regular thing to do wrong with a twitch
• Er lumber room sounds not a regular place
• Unstable enough to make a mistake at one hundred
• Funny oval Scrabble piece that's changeable
• Liable to change unpredictably
• Liable to lead to sudden change
• Not even little by little, a traitor infiltrated
• Likely to blow up rodent about to turn tail
• Capricious boy about to betray one's trust