Whirlpool makes me think of appliances though

Exploding balloon monsters sounds fun, though.
So, for your goblin the _easy_ way would be to make it just automatically deal damage or cost a healing surge when drawn - for example, the goblin could be expressed as ongoing 5 damage (save ends) as it just bites and gnaws on the character, increasing the amount of damage as you get more pieces. Or just that it costs a healing surge to use it for an encounter as it just takes a big chunk of flesh out with a bite.
I'll talk about some more complex ways later... big update today cause of some stuff that happened over on WotC boards:
Old Monsters (corrected to match DMG 184-185 more closely):
Goblin Pyro, Level 1 Skirmisher
[sblock]Goblin Pyro
Level 1 Skirmisher
XP 100
Small natural humanoid
Initiative +3
Senses Perception +0
HP 27; Bloodied 13
AC 15; Fortitude 12, Reflex 14, Will 13
Speed 6

Dogslicer (standard; at-will) * Weapon
+6 vs. AC; 1d6 damage.

Torch (standard; at-will) * Fire
+6 vs. Reflex; 1d4 fire damage and 2 ongoing fire damage (save ends).

Pyromaniac (standard; encounter) * Fire
Range 5/10; +6 vs. Reflex; 1d8 fire damage and 5 ongoing fire damage (save ends). After making this attack, goblin pyro can no longer make Torch attacks. If the goblin pyro misses with this attack and does not roll a 1, make a secondary attack against a random goblin ally within range. Secondary Attack: +8 vs. Reflex; 1d4 fire damage and 2 ongoing fire damage (save ends).
Goblin Tactics (immediate reaction, when a melee attack against the goblin pyro misses; at-will)
The goblin pyro shifts one square away from the attacker.
Danger to Themselves
If a goblin pyro misses with any melee attack and there is an adjacent goblin minion, it kills a goblin minion. If the goblin pyro rolls a 1 on any fire attack roll, it hits itself.
Combat Advantage
The goblin pyro deals an extra 1d6 damage on melee and ranged attacks against any target it has combat advantage against.
Alignment Evil
Languages Common, Goblinoid
Skills Stealth +8, Thievery +8
Str 10 (+0) Dex 17 (+3) Wis 10 (+0)
Con 11 (+0) Int 9 (-1) Cha 12 (+1)
[/sblock]
Earthen Defender, Level 1 Soldier
[sblock]Earthen Defender
Level 1 Soldier
XP 100
Small elemental humanoid
Initiative +0
Senses Perception +0
Earth Control Aura 1; Enemies treat the ground around an earthen defender as hindered terrain.
HP 32; Bloodied 16 (see Crumble)
AC 19 (15 bloodied); Fortitude 15, Reflex 12, Will 12
Speed 5, Burrow 5

Slam (standard; at-will)
+8 vs. AC; 2d6+1 damage
Stuck Weapon (immediate reaction, when damaged by a melee weapon; recharge

)
+6 vs. Reflex; disarm weapon. Weapon is trapped, but may be removed with a successful grapple.
Crumble
A bloodied earthen defender suffers a -4 penalty to AC and drops any stuck weapon.
Alignment Unaligned
Str 13 (+1) Dex 10 (+0) Wis 11 (+0)
Con 16 (+3) Int 8 (-1) Cha 9 (-1)
[/sblock]
New Monsters:
Hobgoblin Deathguard
Level 4 Brute
XP 175
Medium natural humanoid
Initiative +4
Senses Perception +3
HP 68; Bloodied 34
AC 17; Fortitude 18, Reflex 15, Will 16
Speed 6

Halberd (standard; at-will) * Weapon
Reach 2; +7 vs. AC; 1d10 + 4 damage. The hobgoblin deathguard deals +5 damage when within 2 squares of a hobgoblin ally.

Smashing Strike (standard; recharge

) * Weapon
Reach 2; +7 vs. AC; 1d10 + 4 damage and the target is pushed 2 and knocked prone. The hobgoblin deathguard deals +5 damage when within 2 squares of a hobgoblin ally.
Self Sacrifice (immediate interrupt, when adjacent hobgoblin ally is attacked; encounter)
Redirect attack to hobgoblin deathguard and the ally gains a +2 bonus to all defenses until the end of its next turn.
Hobgoblin Resilience (immediate reaction; encounter)
When a hobgoblin suffers an effect a save can end, the hobgoblin makes an immediate save against the effect.
Alignment Evil
Languages Goblinoid
Skills Athletics +11, Intimidate +10
Str 19 (+6) Dex 14 (+4) Wis 12 (+3)
Con 18 (+6) Int 10 (+2) Cha 15 (+5)
Shadow Caller
Level 4 Artillery
XP 175
Medium shadow humanoid (undead)
Initiative +4
Senses Perception +3
HP 45; Bloodied 22
AC 17; Fortitude 18, Reflex 15, Will 16
Immune disease, poison; Resist 10 necrotic; Vulnerable 5 radiant
Speed 6

Shadow Claw (standard; at-will) * Necrotic
+9 vs. Reflex; 1d6 + 4 necrotic damage.

Grasping Shadows (standard; at-will) * Necrotic
+9 vs. Will; 1d8 + 4 necrotic damage. Until the target moves at least 2 squares, it takes 1d8 necrotic damage at the end of its turn.
Shadow Slip (move; recharge

)
Shadow caller gains insubstantial and phasing until the start of its next turn and shifts 3 squares.
Alignment Evil
Languages Common
Skills Intimidate +11, Stealth +12
Str 11 (+2) Dex 16 (+5) Wis 16 (+5)
Con 15 (+4) Int 14 (+4) Cha 19 (+6)
Order of Reason Assassin
Level 6 Lurker
XP 250
Medium natural humanoid
Initiative +4
Senses Perception +3
HP 45; Bloodied 22
AC 17; Fortitude 18, Reflex 15, Will 16
Speed 6

/

ranged

Dagger (standard; at-will) * Weapon
Dagger may be thrown range 5/10; +11 vs. AC; 1d4 + 4 damage.

Locking Garotte (standard; encounter) * Weapon
Requires Combat Advantage; +9 vs. Reflex; 1d4 + 4 damage, ongoing 10 damage and the target is dazed (save ends both, at a -4 penalty). The garotte may also be removed with a Thievery or Strength check against DC 17.

Acid Flask (standard; at-will) * Acid
The assassin may make only 3 acid flask attacks; Range 5/10; +9 vs. Reflex; 1d10 acid damage and ongoing 5 acid (save ends).
Miss: Half damage and no ongoing acid.
Blinding Flash (standard; at-will)
The assassin may only use blinding flash 3 times; She may make a stealth check and shift 3 squares. She does not need concealment or cover to maintain stealth until the end of her turn.
Combat Advantage
She deals an extra 1d6 damage with attacks when she has combat advantage.
Alignment Evil
Languages Common
Skills Bluff +11, Diplomacy +11, Stealth +12, Streetwise +11
Str 11 (+3) Dex 19 (+7) Wis 12 (+4)
Con 14 (+5) Int 16 (+6) Cha 17 (+6)
Equipment 8 daggers, 3 pouches of blinding powder, 3 acid flasks, leather armor, locking garotte
Jungle Giant
Level 10 Skirmisher
XP 500
Large fey humanoid
Initiative +10
Senses Perception +14; low-light vision
HP 108; Bloodied 54
AC 24; Fortitude 24, Reflex 22, Will 22
Speed 7 (forest walk)

Spear (standard; at-will) * Weapon
Reach 2; +15 vs. AC; 1d12 + 6 damage and the target is pushed 1 square.

Poison Javelin (standard; recharge

) * Poison, Weapon
Range 15/20; +15 vs. AC; 1d12 + 6 damage and the giant makes a secondary attack.
Secondary: +13 vs. Fortitude; ongoing 10 poison damage (save ends).
Entangling Ward (immediate interrupt, when an enemy touching the ground moves adjacent; encounter)
Reach 2; +13 vs. Reflex; enemy is restrained until the start of its next turn.
Alignment Unaligned
Languages Elven
Skills Nature +14
Str 22 (+11) Dex 17 (+8) Wis 18 (+9)
Con 20 (+10) Int 10 (+5) Cha 11 (+5)
Angel of Perseverance
Level 11 Controller (Leader)
XP 600
Medium immortal humanoid (angel)
Initiative +9
Senses Perception +10
Aura of Perseverance Aura 5; allies who start their turn in the aura gain 5 temporary hit points and may make a saving throw.
HP 114; Bloodied 57
AC 25; Fortitude 21, Reflex 23, Will 25
Immune fear; Resist 10 radiant
Speed 6, fly 8 (hover)

Longsword (standard; at-will) * Radiant, Weapon
+16 vs. AC; 1d8 + 3 damage and 5 radiant damage.

Overwhelming Word (standard; at-will) * Charm, Psychic
Range 10; +15 vs. Will; 1d6 + 6 psychic damage and the target is dazed (save ends).

Steadfast Blessing (minor; encounter)
Range 10; ally gains a +2 power bonus to saves and all defenses while the angel of perseverance is not bloodied.

Pillar of Radiance (standard; encounter) * Radiant, Zone
Area burst 1 within 10 squares, targets enemies; +13 vs. Fortitude; 1d6 + 6 radiant damage and the target is blinded until the start of its next turn. This power creates a zone for the encounter. Any enemy that enters or starts its turn in the area takes 5 radiant damage and takes a -2 penalty to attack rolls until the start of its next turn.
Alignment Any
Languages Supernal
Skills Religion +12
Str 17 (+8) Dex 19 (+9) Wis 20 (+10)
Con 18 (+9) Int 14 (+7) Cha 23 (+11)
Pain Devil
Level 10 Soldier
XP 500
Medium immortal humanoid (devil)
Initiative +9
Senses Perception +8
HP 106; Bloodied 53
AC 26; Fortitude 23, Reflex 20, Will 22
Resist 20 fire
Speed 6, teleport 4

Razor Scourge (standard; at-will) * Weapon
Reach 2; +17 vs. AC; 2d6 + 5 damage and the target is slowed until the end of its next turn.

Infernal Agony (standard; encounter) * Weapon
Reach 2; +17 vs. AC; 2d6 + 5 damage, ongoing 5 damage, and the target is dazed (save ends both) and knocked prone.
Corrective Lashing (immediate reaction, when an enemy within 6 squares attacks an ally; recharge

)
The pain devil teleports 4 squares towards the enemy and makes a basic attack against the triggering target. If the attack hits, the target is pulled 2 squares and takes ongoing 5 damage (save ends).
Alignment Evil
Languages Supernal
Skills Heal +13, Intimidate +11
Str 21 (+10) Dex 14 (+7) Wis 17 (+8)
Con 18 (+9) Int 12 (+6) Cha 13 (+6)