• humprdinck,
• humperdick,
• humperdinck,
• Humpardink,
• Humberdink,
• humperdank,
• humperdunk,
• humperdenk,
• humpherdink,
• humperedink

• timber,
• jumble,
• humble,
• rumble,
• crumble,
• rumpus,
• dimple,
• bumper,
• thunder,
• tinker,
• dandruff,
• Pumper,
• kinder,
• hinder,
• riddle.

The plural form of the word "humperdink" is "humperdinks". However, please note that "humperdink" is not a commonly used word, and its plural form may not be universally recognized or accepted.

The singular form of the word "humperdink" is still "humperdink". It does not change in the singular form.