Don't Call Me Junior

You'll need to earn Master Relic Hunter which involves completing each of the following quest chains:

The Spirit Forge - Treasure Contract: Gutrek's Cleaver
Taking from the Taker - Treasure Contract: The Infected Orc
The Blessing of Beasts - Treasure Contract: The Thunderlord Sage
The Apexis Device - Treasure Contract: Amulet of Rukhmar
Breaching the Barrier - Treasure Contract: Explosive Discoveries
The Crystal Reborn - Treasure Contract: The Artificer

If he's not in your garrison, you can use the group finder tool to find him. Simply search custom groups for Harrison Jones.

Sallah: Please, what does it always mean, this... this "Junior"?
Professor Henry Jones: That's his name.
[points to himself]
Professor Henry Jones: Henry Jones...
[points to Indy]
Professor Henry Jones: ... Junior.
Indiana Jones: I like "Indiana."
Professor Henry Jones: We named the *dog* Indiana.
Marcus Brody: May we go home now, please?
Sallah: The dog?
[starts laughing]
Sallah: You are named after the dog? Ha, ha, ha... !
Indiana Jones: I've got a lot of fond memories of that dog.

""Exploration Mission Master" removed from "Don't Call Me Junior" meta achievement. UI not updated until a client patch." - Bashiok