Although gestures like it have always been around, Fonzie popularized the thumbs up sign with a positive, "Eyy!" remark that became ubiquitous to his character and is still in use today. The gesture was routinely used by pilots starting in World War II as a signal to their ground-crew. Winkler claimed that he borrowed this from the sign (incorrectly believed in the popular imagination) made at Roman gladiator fights. The term "Eyy!" came from an improvised moment due to Winkler's refusal to constantly comb his hair or have a pack of cigarettes rolled up in his sleeve. Network executives at ABC insisted he make the combing action, but when filmed he instead stopped himself and said the line. It received huge laughs from the audience and the scene was made part of the opening sequence. In the cartoon spin-off of the show the animators were unaware of this, and depicted Fonzie combing his hair in the title. In the series, Fonzie's thumbs-up gesture came to be not only a sign of approval, but also on a few occasions was a quiet gesture of gratitude, his own way of saying "thank you".