Donald O'Connor's last Francis movie.
Donald O'Connor's sixth of six "Francis" movies.
While speaking to Lt. Peter Stirling/Boatswain Mate Slicker Donovan (Donald O'Connor), Francis turns his head for only a moment to a wall, at which point his voice echoes. It appears that as Chill Wills' dubbed in the mule's voice, a rather painstaking detail was considered.
With Donald O'Connor's DUKW (duck) having stalled for want of gasoline, Francis comes along and asks him, "Wanna sell a duck?" This clever play on words was a reference to a catchphrase of the late comedian Joe Penner, "Wanna buy a duck?"