It was interesting to read Charlie's response. I am a native North American English speaker, and I would not recognise any of these expressions.

I have never heard of these, but they made me laugh. I don't know which sausage I would prefer to be called!

British native English speaker here. These would be "terms of endearment" for a much older generation - these are phrases from the 1940s or so. The ones I have heard from my grandparent's generation would be "old sausage" (like "old friend" - two old soldiers meeting each other for the first time in a decade!) and "silly sausage" (an old grandparent telling off a grandchild for doing or saying something a bit stupid!). "Clever" and "little" I have not heard used at all, but "little sausage" could be applied as a term of endearment between two lovers back in the 2nd World War era. It would not be used much now!

Clever sausage - I've never heard this; it may be an old-fashioned way of praising a child's intelligence... Silly sausage - this is a gentle, affectionate way of of telling someone they've done something stupid: usually said by an adult (parent, family member) to a child Little sausage - I haven't heard this one, but it might be an affectionate way of referring to a child - maybe a nickname.. Old sausage - this one seems vaguely familiar - maybe used affectionately by an elderly man to his wife. I'm not sure my wife would be very impressed if I called her this though! (Queen Elizabeth's husband Philip used to call her "cabbage" - apparently.)