Willemijn is renowned worldwide for her portrayal of the character Elphaba in the musical Wicked. She is the only actress to have performed the role in three languages and in four countries. Other theatre credits in Germany include Bat Out of Hell (Sloane), Ghost (Molly Jensen), Tarzan (Kala), Mamma Mia (Donna), Elisabeth (Elisabeth), We Will Rock You (All 3 lead female roles) and Aida (Amneris). In the UK Willemijn also performed in Women on the Verge of a Nervous Breakdown (Paulina).