He absolutely HATES sleeping. He thinks is in absolute waste of time, but the turtles and you can tell that he was going downhill. Mikey: "But... Maybe he isn't tired?"

Leonardo: "This is bad... If we don't get him to sleep, he'll work himself to death." He shivers, noticing how Donnie's droopy eyes were strained.

Donnie: "Ugh, I'm not tired, guys... Quit it." You know Leo was right, you have to make him sleep.