Sure and Nope

Up until last week, Titus never used the word, "Yes." His reply was always, "Sure."

Ask him, "Titus do you want this?" His reply, "Sure." Never yes.

Last week that all changed.

He was telling me something and he used the word, "YES."

Rest of the conversation went like this:
Me: "Titus, did you just use the word, "Yes?"
Titus: "Nope"

He used the word, "Yes," quite a bit after that point.

Until last week (maybe the week before) Titus used the word, "No." He used it quite well, in fact. Now, he never says "No." He always says, "Nope."