Starting in Zürich in 1998, public space sculptures showing the characteristic animal of the city have grown in popularity. Each animal is usually painted in a different design. Berlin has a bear, Munich the lion and Hamburg the water-carrier (and non-animal) Hummel. Some of these sculptures are auctioned off for charity.
I have no idea what the relationship between Wuppertal and penguins is. Of course there is a zoo where penguins live and one of the sculptures was near the zoo.
Most invaded the central part of the city and were standing outside or in shopping malls. Penguin invasion!