After the credits the kangaroo is standing at the peephole and is spraying the K on the screen. Also The kangaroo admires the singers of the closing song while Marc-Uwe is complaining that the kangaroo has to have the final word, to which the kangaroo replied (with its final word): "No, I don't".
The kangaroo is singing along the Warner Brothers fanfare in the opening after which Marc-Uwe Kling is complaining about it.
The opening credits begin with "Starring The kangaroo as itself"
The kangaroo is playing, fighting, reading,exercising etc. during the closing credits.
There is an additional scene in which Marc-Uwe and the kangaroo visits the psychologist.