You need to grind for the "Monkey Organ" first Its in the Rainforest Biome ..just head to Ashlands then take a Left turn . and kill 100 Monkeys for the drop

There's a trick to unlocking that.
First you have to stand outside the zone and hit him with 1000 wooden arrows.
They have to all be wooden or your count starts over.
After the 1000th arrow <give or take, if you reach 1000 just keep going> he stands up on his hind legs and does a little dance Gir style.
After that you can pet him.

I paid Haldor 50 gold coins and he let me take Halstein for a ride around his bubble (including a souvenir picture).

because hes busy chewing on the viking who trys to pet him before you tryed that

Not every domesticated animal likes to be petted :P

He heard about you on the Lox grapevine.