Answer:

RATS

AnswerCrossword Clue
RATS"Doggone!"
RATSCharlie Brown expletive
RATSPied Piper's followers
RATSThey leave the sinking ship
RATS"Darn!"
RATSCharlie Brown's expletive
RATSInformers
RATSResearcher's supply, perhaps
RATS"Oh, drat!"
RATSCharlie Brown's expression
RATSExpression of disgust
RATS"Phooey!"
RATS"Dang!"
RATSPiper's followers
RATSMaze runners
RATSCharlie Brown's oath
RATSWillard's pals
RATS"Peanuts" exclamation
RATS"Peanuts" cry
RATSUnwanted tenants
RATSHamelin undesirables
RATSSome maze runners
RATSHamelin problem
RATSBrown expletive
RATSHamelin headache
RATSCurses!
RATSSqueals
RATSScientific subjects
RATS"What rotten luck!"
RATSPossible Black Death vectors
RATSDesert ... (British WWII division's nickname)
RATS"Darn it!"
RATS"Dagnabbit!"
RATS"Shucks!"
RATSCry from Charlie Brown
RATSTalks
RATSHamelin pests
RATSPied Piper followers
RATSTellers?
RATS"Peanuts" expletive