I am new to nunu, however I just played him two times in a row and both times the enemy team invaded golem, which is odd because it was a normal game. Is it like protocol that you invade enemy nunu;s golem or something? Teams rarely ever do that in normals and extremely rarely twice in a row and I happened to be nunu jungle both times.
It makes sense though because it made it slightly harder to jungle and threw off ganking early game. Just wondering.
Actually because Nunu has consume+smite it makes more sense to not invade a nunu's jungle and instead go around for the red or just try to outclear him. One reason I can think of for an invade, however, isn't for the buff but for kills. Most nunu jungles will grab consume Lvl 1 for the help in jungle, and if you combine that with one or two more weak lvl 1 champs (Fizz, LeBlanc, Caitlyn, etc) then a lvl 1 teamfight that happens to be in your jungle makes a lot of sense. That and some people just like to screw with enemy jungles.
Im no expert when it comes to jungling but im gonna say that it was just coincidence, I am unaware of any standard strat related to Nunu and stealing Golems.
Welcome to the jungle!!!! perhaps you could try to invade your opponent's jungle and steal their blue or red, that is real accomplishment. Remember take
or 
, it could be extremely helpful.
However, if you want a peace jungle, you can ask your teammate to help guard your buffs while the game just get started.
