DUE - Owed or owing.
PEP - To inject with energy and enthusiasm.
PIE - A type of pastry that consists of an outer crust and a filling.
PUP - A young dog, wolf, fox, seal, shark and some other animals.
PIPE - A rigid tube that transports water, steam, or other fluid, as used in plumbing and numerous other applications.
DUPE - To swindle, deceive, or trick.
QUIP - A smart, sarcastic turn or jest; a taunt; a severe retort or comeback; a gibe.
QUID - The inherent nature of something.
EQUIP - To furnish for service, or against a need or exigency; to fit out; to supply with whatever is necessary to efficient action in any way; to provide with arms or an armament, stores, munitions, rigging, etc.; -- said especially of ships and of troops. Dryden.
PIPED - Simple past tense and past participle of pipe.
UPPED - Simple past tense and past participle of up.
PIQUED - Simple past tense and past participle of pique.
QUIPPED - Simple past tense and past participle of quip.