It's a bud!

Yesterday's mystery growth on the Eucalyptus tree down the road has now been identified.
Strange as it may seem, it's nothing more than the flower bud of a  Eucalyptus. Once the red brain-shaped bud with the cross in the middle has grown to about the size of a walnut, the top front 'panel' splits open along the cross lines and falls to the ground, and the large donut circles of fine pollen-tipped stamens inside start to emerge, changing from a lime green to a garish bright yellow in the process.
During the bud-and-flowering process, which the tree is currently right in the middle of, you have the red brain structures and the adjacent yellow flowers spread all over the tree - which for a native Eucalypt, makes a very colourful display. See today's Extra photo.
So after all that, those weird little brain structures are not some sort of unusual fungus, or a curious Eucalypt gall, but rather perform the extremely common function of keeping the tightly furled flowers inside until it's time to open up and fully bloom.
Despite its links to the everyday, it remains a very peculiar bud in its colour, texture and form. While no expert, I'm not exactly a stranger to the huge range of different Eucalyptus species spread all over Australia, and other parts of the world. But really, who's ever seen a bud even remotely like this one? Definitely thin on the ground, these.
I ran another photo of the Eucalypt through the plant identity app, and it came up with quite a wide range of different Eucalypt species as possibilities. But drilling down further into each of those revealed none with the distinctive flower buds in place.
There seems no doubt that it's from the Eucalyptus family, but exactly what species of Eucalyptus I can't determine with any certainty. And that's perfectly OK with me - it's a plant that grows in ordinary suburban environments - including the vacant land just down the road - yet still manages to retain a wee tad of mystery and intrigue.