Confused?
While reconfiguring a Linux gateway recently I managed to get it into a rather confused state, where it thought that its own addresses were unreachable. Attepmting to ping it produced this ICMP message.
20:18:04.441662 2001:770:11d::3 > 2001:770:11d:0:20d:56ff:fe22:320c: icmp6: 2001:770:11d::3 unreachable address
ICMP is usually a pretty dry protocol - I think this is about as funny as ICMP messages come!