Fangoria (long interview):
And when we meet Daddy in the backyard for the first time, he's kind of ambling along like, "Doop-de-doo." You could talk about him being a kind old priest, so he's a little goofy and he's kinda doing these little jokes. And then the sound guys came up with this thing - and I don't know how many people will pick it up - but [the Daddy Long Legs] has a little musical thing he does, like this [Duffield makes alien singing noises], and he's singing back to Kaitlyn the song that she dances to earlier in the movie.
Oh, no shit?
Yeah, because he was probably outside and [heard the song] and thought, "Hey, that's kind of catchy!" So, by singing he's like, "Hey, you remember this song?" A couple of times in the movie you hear, in the distance, him doing that and it's really creepy. He recognizes [Kaitlyn Dever's Brynn] as "the song girl," and then he's so excited! They traveled however many thousands of light years to get here, and he's like, "Okay, we're finally doing our big religious colonization. I'm so excited to be doing this with you! It's so great!" But then Kaitlyn messes it up and embarrasses him.
[Regarding it being dialog-free:]
there were definitely places that were like, "If people are doing their laundry, they're going to get lost immediately." So I'm excited that Hulu looked at it as, "It's going to make people pay attention."