Possible Clues:

• Leaks shouldn't be ignored from this talkative person
• A compulsive talker with balloon?
• I can't shut up a container of helium
• Talkative person making joke about, say, British
• Garrulous one
• One talking excessively
• One who natters a lot
• Person who talks too much - or a balloon
• Talkative person
• Sort who needs to button up