Name: LEGO Cat Birthday Party & Tree House 42666
Brand: Lego
SKU: 42666
Price: 29.99 USD
Availability: InStock

The complete LEGO Friends 42666 Cat Birthday Party Tree House set featuring a two-part build with a treehouse and a separate birthday party area, along with two minifigures, several cat figures, and accessories.

A Feline Festivity

This vibrant build, the LEGO Friends Cat Birthday Party Tree House, captures the entire scene of fun. We've got two main sections: the adventurous multi-level treehouse and the festive party area. Mia and Autumn are right in the thick of it, surrounded by a fantastic cast of animal pals and playful accessories.

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$29.99

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Set # 42666

Released 2025

Pieces 321

Price / Piece 9.3¢

Figures 2

Age 6+

Scale & Brick Value Piece Volume & Pricing Ranks

Piece Rank #870 Top 57% active

Ranked #870 by piece count against 1,543 currently available retail sets.

Historic Scale #3,708 Top 19% of 20,150

Historical ranking across 20,150 cataloged releases since 1949.

Part Efficiency #664 8.9¢/pc • Top 44%

Price-per-piece efficiency rank based on official retail MSRP (8.9¢/piece).

Collector Insights Verified Oct 11, 2026

Includes 2 exclusive molds and 7 rare elements recorded across official inventories.

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Categories: Wildlife & Creatures Pets & Domestic Animals Cats & Felines Buildings & Structures Nature & Country

Set 42666 Build Specifications & Overview

Complete build timeline, spatial dimensions, and display footprint analysis.

Value Breakdown

Est. Build Time (*Pieces per minute): Casual 2.8h 2 ppm*

AFOL (Avg) 1.4h 4 ppm*

Master Builder 0.8h 7 ppm*
Avg Price / Hour: $21.42/hr
Price Per Basic Brick: $0.02

Highly valuable! 73% cheaper than average LEGO sets.

Display Dimensions

Height 17.8 in (45.2 cm) 47 Bricks high

Width 15.2 in (38.6 cm) 48 Studs wide

Depth 10.2 in (25.9 cm) 32 Studs deep

Display Footprint 155.0 sq in (1000.0 sq cm) 48 × 32 Studs

The Scale Check

Height equivalent to approx 11.3 minifigures stacked.

Display Fit

Oversized: Requires Deep Tabletop Surface

Building Instructions

Download or view the official PDF

Set 42666 Minifigures & Parts Manifest

Complete verified inventory of all 0 character and 321 pieces, featuring 1 exclusive part.

Part Categories

Discover the structural DNA and the exact piece types included in this box.

Standard 178 pcs (55.5%)

Greebles 1x1 80 pcs (24.9%)

Technic 17 pcs (5.3%)

Bricks Special 14 pcs (4.4%)

Equipment 10 pcs (3.1%)

Translucent 5 pcs (1.6%)

Slopes Wedges 4 pcs (1.2%)

S N O T 2 pcs (0.6%)

Plates Special 2 pcs (0.6%)

Rare & Exclusive Minifigures

Complete inventory of characters and figures included in this set.

Includes 2 Mini-dolls:

Exclusive Mini-dolls 1
Leo - Red Shirt (fig-016290)

Rare Mini-dolls 1
Paisley - Bright Light Yellow Top (fig-015754)
• Seen in 2 sets ( 42644 )

Includes 6 Animals:

Rare Animals 2
Animal, Cat, Chubby with orange Face, Toes, Medium Blue/Lime Eyes Print (2652pr0003)
• Seen in 2 sets ( 42655 )
Animal, Cat, Chubby with Bright Green Eyes, Light Bluish Grey Fur Print (2652pr0007)
• Seen in 3 sets ( 42688, 6614211 )

Uncommon Animals 2
Animal, Cat, Sitting with Dark Brown Stripes, White Chest, Ears Print (11602pr0010)
• Seen in 5 sets (incl. 42669, 42670, 42691, 42704)
Animal, Cat, Kitten Sitting with Open Eyes, White Mouth, Nougat Paws Print (69902pr0003)
• Seen in 4 sets (incl. 42671, 42691)

Common Animals 2
Animal, Fish [Hollow Stud Mouth] (64648)
• Seen in 76 sets
Animal, Cat, Kitten Sitting with Yellow Eyes, Dark Pink Tongue Print (69902pr0004)
• Seen in 7 sets

Rare & Exclusive Parts

Track this build's most elusive bricks and their production history.

Exclusive Parts 1 piece
Coral Brick Curved 2 x 1 with Inverted Cutout (SKU: 78666)

Rare Parts 4 pieces
White Animal, Cat, Chubby with orange Face, Toes, Medium Blue/Lime Eyes Print (SKU: 2652pr0003)
• Seen in 2 sets ( 42655 )
Lime Plant, Leaves Stacked 4 x 5 x 1 2/3 (SKU: 5058)
• Seen in 2 sets ( 42669 )
Dark Bluish Gray Animal, Cat, Chubby with Bright Green Eyes, Light Bluish Grey Fur Print (SKU: 2652pr0007)
• Seen in 3 sets ( 42688, 6614211 )
Bright Pink Plate Special 4 x 4 with 3 x 3 Quarter Round Cutout (SKU: 35044)
• Seen in 3 sets ( 31169, 77078 )

Uncommon Parts 8 pieces
Bright Green Animal Body Part, Barb / Claw / Tooth / Talon / Horn, Small (SKU: 53451)
• Seen in 4 sets (incl. 31215, 72042, 21366)
Coral Brick Arch 1 x 4 x 2 (SKU: 6182)
• Seen in 4 sets (incl. 30697, 42640, 42674)
Nougat Animal, Cat, Kitten Sitting with Open Eyes, White Mouth, Nougat Paws Print (SKU: 69902pr0003)
• Seen in 4 sets (incl. 42671, 42691)
Medium Brown Animal, Cat, Sitting with Dark Brown Stripes, White Chest, Ears Print (SKU: 11602pr0010)
• Seen in 5 sets (incl. 42669, 42670, 42691, 42704)
Bright Pink Brick Round 2 x 2 Dome Bottom [Open Stud] (SKU: 15395)
• Seen in 5 sets (incl. 42661, 11212, 11214)
Blue Plate Special Round 1 x 2 Half Circle with Stud (Jumper) (SKU: 1745)
• Seen in 5 sets (incl. 11205, 60464, 60475)
Bright Pink Container Box 2 x 2 x 1 Reinforced Bottom (SKU: 2821)
• Seen in 5 sets (incl. 75681, 75683, 42655, 43273)
Bright Light Yellow Wool / Yarn (SKU: 6900)
• Seen in 5 sets (incl. 42640, 42655, 42665, 42670)

Color Insights & Harmony

Complete chromatic distribution, dominant shades, and cross-set color matching.

Hex: Count: Share:

Included Palette

The complete chromatic blueprint and exact piece counts defining this set's look.

41 pcs (13.1%) Tan

35 pcs (11.2%) Bright Green

26 pcs (8.3%) Medium Azure

25 pcs (8.0%) Yellowish Green

18 pcs (5.8%) White

18 pcs (5.8%) Bright Pink

17 pcs (5.4%) Reddish Brown

15 pcs (4.8%) Lime

12 pcs (3.8%) Blue

11 pcs (3.5%) Coral

11 pcs (3.5%) Bright Light Orange

11 pcs (3.5%) Dark Orange

8 pcs (2.6%) Bright Light Blue

7 pcs (2.2%) Medium Nougat

6 pcs (1.9%) Black

6 pcs (1.9%) Red

5 pcs (1.6%) Dark Pink

5 pcs (1.6%) Light Bluish Gray

4 pcs (1.3%) Light Aqua

3 pcs (1.0%) Lavender

3 pcs (1.0%) Dark Turquoise

3 pcs (1.0%) Bright Light Yellow

3 pcs (1.0%) Medium Lavender

3 pcs (1.0%) Yellow

3 pcs (1.0%) Trans-Light Blue

2 pcs (0.6%) Green

2 pcs (0.6%) Pearl Gold

2 pcs (0.6%) Orange

1 pcs (0.3%) Medium Brown

1 pcs (0.3%) Flat Silver

1 pcs (0.3%) Magenta

1 pcs (0.3%) Dark Bluish Gray

1 pcs (0.3%) Trans-Orange

1 pcs (0.3%) Nougat

1 pcs (0.3%) Trans-Yellow

The Mix

A proportional breakdown of the defining colors shaping this set's aesthetic.

35 Colors

Matching Sets

Kapp'n's Island Boat Tour SKU: 77048 • Released 2024 93.9% Match Animal Vet Clinic SKU: 42696 • Released 2026 87.3% Match The Turtle Beach House SKU: 21254 • Released 2024 85.9% Match Bunnie's Outdoor Activities SKU: 77047 • Released 2024 85.4% Match

Green Toad SKU: 71413 • Released 2023 91.5% Match

Autumn’s Room SKU: 42646 • Released 2025 86.9% Match

Panda SKU: 6173 • Released 2012 86.2% Match

Cars and Trucks Brick Box SKU: 10439 • Released 2024 85% Match

Apiary SKU: 562412 • Released 2024 84.9% Match

Stephanie's Summer Play Cube SKU: 41411 • Released 2020 84.8% Match

42666 Set Valuation

Projected post-EOL market performance and condition-based compound growth estimates.

Base Brand

Retail MSRP (Base)

$30

Original catalog price

5-Year Est. (Sealed Post-EOL)

$57 — $66

Variance model adjusted

Estimated ROI

+104.9%

Expected mid-range hold

Want custom year projections, condition adjustments, or unboxed values? Open ValueMySet

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LEGO Cat Birthday Party & Tree House 42666