Ach Egon! (1961)

Pediatrician Waldemar Weber is at his wits' end. Of all days, his adopted son Egon—from his first marriage, whom Waldemar has always kept a secret from his young wife Henny—has announced he’s coming to visit on their first wedding anniversary. Waldemar must stop Egon at all costs. When Egon finally shows up at the door, he turns out to be a monkey trainer.