It's a/an elf.
an
It's a/an yellow car.
a
It's a/an old teddy bear.
an
It's a/an elephant.
an
It's a/an new kite.
a
It's a/an long train.
a
It's a/an short blue train.
a
It's a/an big orange robot.
an
It's a/an small green plane.
a
It's a/an ugly monster.
an
It's a/an beautiful doll.
a
It's a/an apple.
an