Penis bear is a very insulting term used against old people. How ever if you know the old person, penis bear can be an endearing term.
You can insult your grandparents or you can insult old people on the street. For example if you see an old person walking down the street you can say "Hey Penis Bear! shouldn't you be dead by now???" Or "Hey penis bear you are older than dirt"!!! By saying penis bear the elder understands that you are talking to them. However if you know the elder you can use it as an endearing term. For example you can say "Hey Penis Bear how you been?" or "I love you so much my shriveled up old penis bear"