The party is certainly shocked to find out that the normal sized humanoid they thought that they knew was in fact, two goblins in a trench coat.  However, these sneaky industrious finks have found a way to make this odd situation work to their advantage.

Too Many Hands

Starting at 3rd level, you can have advantage on Steal (sleight of hand) checks.

PANIC!

When you choose this archetype at 3rd level, Whenever you take damage you can use your reaction to split and go in two directions at once. This grants you the effects of disengage and allows both goblins to move up to the full movement speed each. 

While split each Goblin has half of the remaining hit points.  They still share the same initiative and do not get any more attacks than normal (They are still only one character), but so long as both have weapons either one can attack. While split they count as an ally for the purpose of sneak attack.  Attacks of opportunity against them have disadvantage.  They cannot regain Hit Points by any method until they use one action to rejoin.

Cut some eye-holes!

Starting at 9th level, you have advantage on all Perception and Investigation checks.  You may also use Goblin Dark vision if the race they were posing as didn't already have better than 60 feet night vision.  You also cannot be surprised.

While separated through "PANIC!" they loose advantage, but their total modifier for all Intelligence(Investigation) checks and Wisdom(Perception) Checks are doubled.

Bickering!

By 13th level, you goblins have grown different enough that they have learned new skills.  Gain proficiency in three new skills.

While the goblins are split using "PANIC!" Their constant arguing is enough to confound any foe.  use a bonus action to force enemies to make a wisdom saving throw.  The DC is 8+Proficiency bonus+Charisma.  Unless they have proficiency is performance, persuasion, or deception, then they may double they may calculate the DC as 8+Proficiency+(one of Performance, persuasion, or deception).  On a failed save, the target has a disadvantage on all attack rolls.  On a successful save, they enemy has disadvantage on attack rolls against all targets except your goblins.  They may make a new Save at the end of each turn.  if the target makes their save AFTER having failed their save at least once, the will automatically succeed on saves against this effect for the next 24 hours.

GOTCHYA!

When you reach 17th level, you have become adept at playing off people's surprise at your strange nature.  When you attempt to attack a creature, it must make a wisdom saving throw versus 10 + your charisma bonus  UNLESS you have Expertise in Performance or Deception, then the DC is calculated as 8 + Charisma Bonus + proficiency.

On a failed save you have advantage against the target

On a successful save, the creature perceives your nature and has disadvantage to hitting you the next round.