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LEGO Missing Piece Checker

Rule out the usual hiding places first. If the piece really is gone, check the set piece by piece and leave with the element ID LEGO asks for, or a link to buy the part.

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42666 Cat Birthday Party & Tree House

313 pieces in 138 part and color combinations, plus 2 minifigures.

The official piece count includes the 8 parts inside the set's minifigures, which this inventory lists separately. Spare parts are counted in neither figure.

Before you call it missing

Builders who report a missing piece often find it in one of these places. Tick each one off as you look.

Every bag and the box. Shake out each bag, check its corners and seams, and look inside the empty box.
Inside what you have built. Small pieces lodge inside tubes, under plates and between studs. Turn the model over and look.
The last few steps. Compare each recent step with its parts callout. A piece used in the wrong place earlier leaves you one short later.
Look-alike colors. 1 part in this set come in two colors that are easy to mix up; they are listed below.
The spare pieces. This set comes with 26 spare pieces, marked on each row of the checklist. One may be the piece you need.
The floor and your building area. Check under furniture, the chair and the edges of your building surface.

Look-alike colors in this set

These parts appear in this set in two colors that are easy to confuse. If you are one short in one color, check whether it went in where the other color belongs. Each color has its own element ID in the parts list at the back of the instructions.

Tile 1 x 2 with Groove Dark Turquoise ×2 Medium Azure ×4 Dark Turquoise is darker than Medium Azure.

Piece checklist

Medium Azure 26 pieces

Brick 1 x 1 Medium Azure Part 3005 Element 6603285 or 4619652 ×5
Brick 1 x 4 Medium Azure Part 3010 Element 6603319 or 6036238 ×2
Brick Arch 1 x 6 x 2 - Thin Top without Reinforced Underside [New Version] Medium Azure Part 15254 Element 6603333 or 6059179 ×1
Brick Curved 1 x 3 x 2 Inverted [Inside Bow] Medium Azure Part 18653 Element 6357619 ×2
Plate 1 x 10 Medium Azure Part 4477 Element 6603595 or 6423273 ×3
Plate Round 2 x 2 with Axle Hole Type 1 (+ Opening) Medium Azure Part 4032a Element 6109752 ×2
Plate Special 2 x 2 with Groove and Center Stud (Jumper) Medium Azure Part 87580 Element 6126090 or 6003008 ×5
Tile 1 x 2 with Groove Medium Azure Part 3069b Element 6603315 or 4649741 Also in Dark Turquoise ×4
Tile Round 1 x 2 Half Circle Medium Azure Part 1748 Element 6510074 or 6445337 1 spare in the box ×2

Yellowish Green 25 pieces

Plant, Plate 1 x 1 Round with 3 Leaves Yellowish Green Part 32607 Element 6541652 ×25

Bright Pink 18 pieces

Brick Round 2 x 2 Dome Bottom [Open Stud] Bright Pink Part 15395 Element 6541655 ×2
Brick Round 2 x 2 Dome Top with 2 Ears Bright Pink Part 5690 Element 6513944 or 6483520 ×2
Container Box 2 x 2 x 1 Reinforced Bottom Bright Pink Part 2821 Element 6517936 ×3
Plate Round 1 x 1 with Solid Stud Bright Pink Part 6141 Element 4517996 1 spare in the box ×4
Plate Round 2 x 2 with Axle Hole Type 1 (+ Opening) Bright Pink Part 4032a Element 6498749 ×3
Plate Special 2 x 2 with Groove and Center Stud (Jumper) Bright Pink Part 87580 Element 6251842 ×1
Plate Special 4 x 4 with 3 x 3 Quarter Round Cutout Bright Pink Part 35044 Element 6526012 ×1
Tile 2 x 2 with Groove Bright Pink Part 3068b Element 4615728 ×2

Reddish Brown 17 pieces

Bar 1L with Clip [Cut Edges and One Side Hole] [Full Clip] Reddish Brown Part 3484 Element 6439053 ×2
Bar 2L with Stop in Center Reddish Brown Part 78258 Element 6451002 1 spare in the box ×2
Bar Holder with Hole and Bar Handle Reddish Brown Part 23443 Element 6476174 ×1
Brick Sloped 33° 3 x 2 Reddish Brown Part 3298 Element 4216625 ×1
Equipment Candlestick Reddish Brown Part 37762 Element 6422088 ×6
Large Figure Weapon Lightsaber Hilt with Axle Hole and Two Bar Holders Reddish Brown Part 24122 Element 6459423 ×2
Plate Round 1 x 1 Swirled Top / Poo Reddish Brown Part 53119 Element 6438899 or 6275030 1 spare in the box ×1
Plate Special 1 x 2 with Clip Vertical on End Reddish Brown Part 78256 Element 6459597 ×1
Technic Brick 1 x 2 [1 Pin Hole] Reddish Brown Part 3700 Element 4211252 ×1

Lime 15 pieces

Headwear Accessory Hat with Small Pin, Cap Lime Part 6913 Element 6509777 1 spare in the box ×1
Plant, Leaves 4 x 3 Lime Part 2423 Element 6268818 or 6094069 ×8
Plant, Leaves Stacked 4 x 5 x 1 2/3 Lime Part 5058 Element 6522798 ×3
Plate 6 x 10 Lime Part 3033 Element 6289699 or 4172875 ×2
Plate Round Corner 6 x 6 Lime Part 6003 Element 6129601 ×1

Blue 12 pieces

Brick Special 1 x 1 with Studs on 2 Sides Blue Part 47905 Element 6531923 or 4213570 ×1
Cupboard 2 x 3 x 2 with Hollow Studs Blue Part 92410 Element 6313992 or 4619667 ×1
Dish 2 x 2 Inverted [Radar] Blue Part 4740 Element 4570283 or 4239188 ×2
Plate Round Corner 6 x 6 Blue Part 6003 Element 6093691 or 4240399 ×2
Plate Special Round 1 x 2 Half Circle with Stud (Jumper) Blue Part 1745 Element 6533009 ×1
Plate Special Round 2 x 2 with Center Stud (Jumper Plate) Blue Part 18674 Element 6194417 ×2
Tile 2 x 3 Blue Part 26603 Element 6196596 ×2
Wedge Plate 2 x 4 Blue Part 51739 Element 4609454 ×1

Bright Light Orange 11 pieces

Brick 1 x 1 Bright Light Orange Part 3005 Element 6061685 or 4490694 ×3
Brick 1 x 2 Bright Light Orange Part 3004 Element 6003003 or 4490695 ×3
Brick Arch 1 x 4 Bright Light Orange Part 3659 Element 6071607 ×1
Brick Curved 2 x 1 with Inverted Cutout Bright Light Orange Part 78666 Element 6392166 ×2
Container Box 2 x 2 x 1 Reinforced Bottom Bright Light Orange Part 2821 Element 6439231 ×1
Tile 2 x 2 with Groove Bright Light Orange Part 3068b Element 6020147 or 4525871 ×1

Coral 11 pieces

Brick 1 x 1 Coral Part 3005 Element 6422915 or 6264956 ×3
Brick 1 x 2 Coral Part 3004 Element 6258572 ×3
Brick Arch 1 x 4 x 2 Coral Part 6182 Element 6519696 ×1
Brick Curved 2 x 1 with Inverted Cutout Coral Part 78666 Element 6541654 ×2
Tile 2 x 2 Curved, Macaroni Coral Part 27925 Element 6250024 ×2

Dark Orange 11 pieces

Antenna 1 x 4 with Flat Top Dark Orange Part 3957b Element 6514016 or 6400293 1 spare in the box ×1
Brick 1 x 2 Dark Orange Part 3004 Element 4579659 or 4164441 ×3
Brick 2 x 3 Dark Orange Part 3002 Element 6536259 or 4597487 ×1
Plate 1 x 1 x 2/3 with Open Stud Dark Orange Part 86996 Element 6382577 ×1
Plate 1 x 2 Dark Orange Part 3023 Element 4570877 or 4162217 ×5

Bright Light Blue 8 pieces

Animal, Fish [Hollow Stud Mouth] Bright Light Blue Part 64648 Element 6195347 ×1
Brick Curved Inverted 2 x 2 x 2/3 Bright Light Blue Part 32803 Element 6336860 ×2
Brick Sloped 30° 1 x 1 x 2/3 (Cheese Slope) Bright Light Blue Part 54200 Element 6372124 1 spare in the box ×2
Brick Special 1 x 1 with Headlight Bright Light Blue Part 4070 Element 6387434 ×2
Brick Special 1 x 2 with 1 Center Stud on 1 Side, Bottom Stud Holder Bright Light Blue Part 86876 Element 6522315 ×1

Medium Nougat 7 pieces

Plate Round 2 x 2 with Axle Hole Type 1 (+ Opening) Medium Nougat Part 4032a Element 6167643 ×1
Tile Round 1 x 1 with Animal Track Print Medium Nougat Part 98138pr0056 Element 6287856 or 6152676 1 spare in the box ×6

Black 6 pieces

Animal, Cat, Kitten Sitting with Yellow Eyes, Dark Pink Tongue Print Black Part 69902pr0004 Element 6520727 ×1
Bar 5L with Handle (Friction Ram) Black Part 87618 Element 4623113 ×1
Equipment Candlestick Black Part 37762 Element 6290456 ×1
Hose Rigid 3mm D. 9L / 7.2cm Black Part 75c09 Element 6409912 or 4614226 ×1
Plate Special Round 1 x 1 with Hollow Stud and Horizontal Bar 1L Black Part 32828 Element 6196548 1 spare in the box ×1
String with End Studs 11L Overall Black Part 14226c11 Element 6096955 or 6037558 1 spare in the box ×1

Red 6 pieces

Technic Axle 2 Notched Red Part 32062 Element 4142865 ×6

Dark Pink 5 pieces

Plate Special Round 2 x 2 with Center Stud (Jumper Plate) Dark Pink Part 18674 Element 6223767 ×4
Wool / Yarn Dark Pink Part 6900 Element 6509764 ×1

Light Bluish Gray 5 pieces

Plate 2 x 2 Light Bluish Gray Part 3022 Element 4211397 ×1
Technic Axle Connector Hub with 3 Axles at 120° Light Bluish Gray Part 57585 Element 4502595 ×3
Technic Pin 1/2 without Friction Ridges Light Bluish Gray Part 4274 Element 4274194 or 4211483 1 spare in the box ×1

Light Aqua 4 pieces

Plant, Flower with 5 Pointed Petals and Pin Light Aqua Part 18853 Element 6500671 2 spares in the box ×1
Plate 2 x 3 Light Aqua Part 3021 Element 6426724 or 6192108 ×1
Tile 1 x 2 with Cat Food Box, Cat, White 'MEOW BITS' Print Light Aqua Part 3069bpr9932 Element 6527761 ×2

Bright Light Yellow 3 pieces

Plant, Flower, Plate Round 1 x 1 with 5 Petals Bright Light Yellow Part 24866 Element 6426463 1 spare in the box ×2
Wool / Yarn Bright Light Yellow Part 6900 Element 6522800 ×1

Dark Turquoise 3 pieces

Brick Special 1 x 2 x 1 2/3 with 4 Studs on 1 Side Dark Turquoise Part 22885 Element 6513765 ×1
Tile 1 x 2 with Groove Dark Turquoise Part 3069b Element 6213779 or 4164140 Also in Medium Azure ×2

Lavender 3 pieces

Headwear Accessory Bow with Heart, Long Ribbon and Pin Lavender Part 11618 Element 6023826 1 spare in the box ×1
Plant, Flower, Plate Round 1 x 1 with 5 Petals Lavender Part 24866 Element 6214235 1 spare in the box ×2

Medium Lavender 3 pieces

Plant, Flower, Peony Rose with 2 Layers Medium Lavender Part 5904 Element 6550818 or 6519102 ×2
Plate 2 x 4 Medium Lavender Part 3020 Element 4619516 ×1

Trans-Light Blue 3 pieces

Cone 1 x 1 [Top Groove] Trans-Light Blue Part 59900 Element 6514027 or 6337639 ×1
Dish 2 x 2 Inverted [Radar] Trans-Light Blue Part 4740 Element 6580378 or 6245307 ×1
Plate Round 1 x 1 with Solid Stud Trans-Light Blue Part 6141 Element 6514058 or 6240225 1 spare in the box ×1

Yellow 3 pieces

Brick Round 4 x 4 Centre Hole Yellow Part 87081 Element 6490950 or 6310222 ×1
Plate Special 2 x 2 with Groove and Center Stud (Jumper) Yellow Part 87580 Element 6126050 or 4565386 ×1
Plate Special 4 x 4 with 3 x 3 Quarter Round Cutout Yellow Part 35044 Element 6474986 ×1

Green 2 pieces

Plate Special 1 x 2 with Bar Up [Horizontal Arm 5mm] Green Part 88072 Element 6261358 or 6073022 ×2

Orange 2 pieces

Plate 2 x 4 Orange Part 3020 Element 4158355 or 4122468 ×2

Pearl Gold 2 pieces

Headwear Accessory Crown / Tiara Pearl Gold Part 33322 Element 6605929 or 6173109 1 spare in the box ×1
Headwear Accessory Hat with Small Pin, Clown / Party with Pin Pearl Gold Part 24131 Element 6287612 or 6220929 ×1

Dark Bluish Gray 1 piece

Animal, Cat, Chubby with Bright Green Eyes, Light Bluish Grey Fur Print Dark Bluish Gray Part 2652pr0007 Element 6542233 ×1

Flat Silver 1 piece

Equipment Shovel [Rounded Handle End] Flat Silver Part 3837 Element 6210601 or 6038687 ×1

Magenta 1 piece

Plate 8 x 8 with Rounded End Magenta Part 41948 Element 6349472 ×1

Medium Brown 1 piece

Animal, Cat, Sitting with Dark Brown Stripes, White Chest, Ears Print Medium Brown Part 11602pr0010 Element 6520143 ×1

Nougat 1 piece

Animal, Cat, Kitten Sitting with Open Eyes, White Mouth, Nougat Paws Print Nougat Part 69902pr0003 Element 6542234 ×1

Trans-Orange 1 piece

Wave / Flame Small with Pin Trans-Orange Part 37775 Element 6514274 or 6357747 1 spare in the box ×1

Trans-Yellow 1 piece

Tile Round 1 x 1 Trans-Yellow Part 98138 Element 6514193 or 6274740 1 spare in the box ×1

[No Color/Any Color] 1 piece

Sticker Sheet for Set 42666-1 [No Color/Any Color] Part 10113040 Element 6542237 ×1

Minifigures 2 figures

Paisley - Bright Light Yellow Top, Medium Lavender Skirt Minifigure, checked as a whole figure ×1
Leo - Red Shirt, Yellow Shorts Minifigure, checked as a whole figure ×1

Tick each piece as you find it, or mark it missing.

When a piece really is missing

Ask LEGO

LEGO takes requests for pieces missing from a new set through its customer service site. The form asks for the set number and each piece's element ID, the number printed beside the piece in the parts list at the back of the instructions. This checker lists both.

Request a replacement from LEGO

Buy the piece

Mark a piece missing and your list links it to an eBay search for that part, which also covers pieces from older or second-hand sets.

Keep a record

Copy or download your missing list (the CSV opens in any spreadsheet), or print the whole checklist and tick pieces off on paper. Your marks stay in this browser, so you can check a big set over several sittings.