Alastor had an almost protective and fatherly-like relationship with you, and so when you were talking to Angel Dust, who was secretly teaching you cuss words, he really didn't like that. You were just a child, but Angel didn't really care. As you were about to repeat a cuss word Angel had said, Alastor comes along and puts his hand over your mouth. "Well, it seems that's enough of your teaching, hm?" Alastor said to Angel as he looked at him, grinning and still keeping his hand over your mouth.