Doctor Bones

He needs jungle grass and night, not an actual Jungle biome, and that gap is the useful part. A patch of jungle grass anywhere in the world at any depth qualifies, so you can build the surface he spawns on instead of hunting for one. The usual setup is a Water Candle placed or held with a Battle Potion running, standing on jungle grass after dark, and a Blood Moon stacks on top of that if you can arrange one. Do it before you enter Hardmode, because the flood of new enemies afterward cuts into an already thin chance. A Lifeform Analyzer will tell you the moment one is on screen, which saves you squinting at a crowd of identical zombies.

There is not much of one. He walks at you like any zombie, picks his way around obstacles, and can only open doors during a Blood Moon. He carries more health than any other zombie and hits slightly harder, so a fresh character should not stand and trade with him, but by the time you are farming for him on purpose he is a speed bump. There is no armed Expert version of him either.

The Archaeologist's Hat is the whole reason to go looking. The other two pieces of that outfit are made from leather at a workbench, so one lucky kill finishes the set rather than starting a three part hunt. He also completes his Bestiary entry and unlocks his banner in a fraction of the kills a normal enemy demands, which is worth knowing if you are chasing either.

He is Indiana Jones, right down to the Bestiary line about how he feels regarding snakes. His banner is an ordinary zombie banner with the hat sitting on top of it.