Thirty, or 30, is a Numberblock made of 30 blocks.
Arifmetix's design of Thirty is white with yellow borders (10x3), 3 decagram eyes in the colours of the first 3 Numberblocks (3x10), and gloves with 3 stars on each ((3x5)x2=15x2=30)
PBS66Wikia's design has three ten-blocks with yellow borders, six red star eyes, a jester's hat, six hands and gloves, and is arranged 5x6.
Jamil's Thirty doesn't have much details but he has a array display, which means he is a super rectangle.
Zero, One, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Eleven, Twelve, Thirteen, Fourteen, Fifteen, Sixteen, Seventeen, Eighteen, Nineteen, Twenty, Twenty-One, Twenty-Two, Twenty-Five, Thirty, Forty, Fifty, Sixty, Seventy, Eighty, Ninety, One Hundred, One Thousand, Ten Thousand, One Hundred Thousand, One Million
Big Bad Square, The Terrible Twos, Octoblock, The Three Threes, Octonaughty, Step Squad, The Four Fours
Twenty-Three, Twenty-Four, Thirty-Five, Thirty-Six, Forty-Two, Forty-Nine, Sixty-Four, Ninety-Nine, Two Hundred, Three Hundred
Flapjack Snaffler, Blockzilla, Big Tum
Fluffies, Squarey, Numberblobs, Aliens, Rainbows, Flatlanders, Alphablocks