Unbirthday Party

Whenever a creature enters the battlefield under your control Bizarre X where X is the number of
creatures you control.
"Now, statistics prove that you've one birthday, just one birthday every year!"
"Ah, but there are three hundred and sixty four unbirthdays!"
"Precisely why we're gathered here to cheer!"
"Then today is my unbirthday too!"
"A very very happy unbirthday to you!