It has 12 squares.
No. He dressed up as Pentominos.
12, if you count reflections as the same figure.
Pentominoes are all the flat figures you can make with five squares (connected by their sides). There are 12 in total.
You can make 12 different shapes (counting flips) with 5 squares set orthogonally (not diagonally). These are called pentominos.
A polyomino (no e!) is a shape made of n squares fit together. They must connect with edges. One example is the Tetris pieces. They are all tetrominos, which have 4 sqaures. pentominos havbe five, dominoes have 2, triminos have 3, ect.