Carroll replied that he was "just joking", and took the note back before leaving the museum.
Later that day, Carroll went to a KFC restaurant in Wellington and ordered a meal, paying with a fake $50 note.
The staff member accepted the note and gave change.
Carroll then returned to the same restaurant and spent a second counterfeit $50 note, again receiving a meal and change.
Questioned later by police, Carroll said he had received the notes from his cousin and "thought he'd see if he could use them".
Judge Jan Kelly said they were "serious charges, carrying a maximum of seven years' imprisonment".
She said Carroll was currently serving a sentence of community detention for theft, and had a history of burglary, theft and fraud.
The judge sentenced Carroll to four months' community detention, from 7pm to 7am seven days a week, beginning on September 6, when his current sentence ends.
Carroll was also ordered to pay $100 reparation.