People who come into a bar for the sole reason that have nowhere else to go and are basically waiting to die. Ususally these people have no lives, jobs or friends and rely people who are not aware of what social leeches they are and accidentally engage them in conversation.
New guy just sat down next to that walking obituary who is actually knitting at the end of the bar and won't shut up about her 12 dead husbands and having to put her cat down.
To be in a delicate situation; to be on the edge of danger or ruin.
An 'eggshell' is the thin, white outer coating of an egg. The shell is very thin and breaks easily. So if you are 'walking on eggshells' you are in a situation where you could break something (or get in trouble or ruin everything) very easily.