In this talk we will discuss different aspects of the Cauchy problem of a class of fourth order thin film equation of the form . We will show recent results in which we obtained a countable number of similarity solutions of the thin film equation via a homotopy transformation as to the similarity solutions of the classic bi-harmonic equation . Also, another similar homotopic approach is performed directly from the thin film equation to the parabolic bi-harmonic equation in order to obtain important properties for the Cauchy problem. This is a joint work with Prof. Victor. A. Galaktionov at the University of Bath (UK).