Avengers: Age Of Ultron - 32 Easter Eggs, In-Jokes And References

As Hulk and Iron Man face off in South Africa, they destroy the environment - including bringing down an entirely building (complete with a Stark quip asking how quickly he could buy it) - and there's a quick glimpse of a truck with "Crawford" emblazoned on the side.

That could well be a reference to Dr Geoffrey Crawford, Bruce Banner's mentor who turned villain when his body began to fail and he saw Hulk's genetics as a means to lengthen his life. Having turned into the super-intelligent Hulk-like Ravage, Crawford fought off both Hulk and a Hulkbuster unit on a rampage, before he was ultimately bested.