Duo blinked, bit his lip, and cracked up completely. The quote was funny on its own, and the voice was hysterical, but it was Dick's reaction that finished him completely.
It was a good thing Dick was there to lean on, or Duo might've fallen over and done his head considerable damage.
Kisame laughing didn't much help, either. He had a very infectious laugh for a shark-man-ninja.
"I... love... my... gundam," Duo managed, around semi-hysterical giggles. "Chum!"