Dodger

To get [item=180645] you have to find [npc=171206] in Ardenweald,
it will make an action on which you'll have to reply with emote in chat.
After each successful interaction it will despawn and you'll have to find him again
until you make him your pet ([item=180645]) - 5 times in total.
To find [npc=171206] you have to search around the critters of the same type,
it spawns near Vulpins in the Ardenweald: [npc=166973], [npc=161920],
[npc=165809], [npc=172723], [npc=170069], [npc=160729]...
To make it easier make a macros:
/tar Playful Vulpin
/run SetRaidTarget("target", 1)

Vulpin locations i found running around Ardenweald:

Spoiler

/way 40.75 27.47 Vulpin
/way 40.82 51.42 Vulpin
/way 41.27 49.72 Vulpin
/way 50.99 54.63 Vulpin
/way 46.49 66.53 Vulpin
/way 32.09 43.20 Vulpin
/way 64.32 29.50 Vulpin
/way 63.28 26.16 Vulpin
/way 66.42 31.12 Vulpin
/way 72.38 31.41 Vulpin
/way 70.48 29.70 Vulpin
/way 67.81 32.06 Vulpin
/way 67.19 28.87 Vulpin
/way 64.93 22.92 Vulpin
/way 48.50 59.19 Vulpin
/way 43.05 64.96 Vulpin
/way 44.17 66.64 Vulpin
/way 36.10 49.68 Vulpin
/way 33.02 43.99 Vulpin
/way 69.06 30.31 Vulpin

Vulpin Action

Emote to use

Playful Vulpin begins to dig curiously.

/curious

Playful Vulpin wanders around unable to sit still.

/sit

Playful Vulpin sings all alone.

/sing

Playful Vulpin dances with joy.

/dance

Playful Vulpin sits down lonely and sad.

/pet

The locations [npc=171206] spawned for me:

/way 40.71 27.46 Playful Vulpin
/way 70.31 29.60 Playful Vulpin
/way 41.27 28.74 Playful Vulpin
/way 69.02 30.37 Playful Vulpin
/way 34.10 44.99 Playful Vulpin
Video: https://youtu.be/-NL85ACDp-c

Also check Unholypriest post for more locations
Looks like it spawns more in the upper part of the zone so check there first.

Zone: Ardenweald
Treasures of Revendreth --> Playful Vulpin Befriended

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  Playful Vulpin Befriended is part of the achievement Treasures of Revendreth. To be able to complete this, a [npc=171206] must be found in the Ardenweald. You have to perform 5 different interactions with him. The problem is, he disappears after each emotion and you have to search for him again.
  
  
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  It's best to make a macro, that makes the search easier:
  /cleartarget
  /tar Playful Vulpin
  
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  Here are the actions that need to be performed: for example, if the chat says Playful Vulpin begins to dig curiously, then type into the chat /curious or use the related emote.
  1. - begins to dig curiously = /curious
  2. - wanders around unable to sit still = /sit
  3. - sings all alone = /sing
  4. - dances with joy = /dance
  5. - sits down lonely and sad = /pet
  
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  One other little note:
  - keep [npc=171206] in focus when doing the emote.
  - It is best to dismount from the mount. But for me it also worked when I was sitting on the mount.
  
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After the last action the playful Vulpin jumps into your arms and you get the [item=180645] = [npc=171247].

Here are some spawn points:
/way 34.11 44.88
/way 40.71 27.46
/way 41.23 28.77
/way 50.70 55.10
/way 51.00 54.00
/way 51.20 55.10
/way 67.53 31.89
/way 69.05 30.31
/way 70.31 29.64
/way 72.41 31.56

I show you the way to some locations in this Video: https://youtu.be/W8KIKu9Rm-k