Sometimes I worry (without sufficient evidence) that the guy is having a tough time at school. Yesterday, it was because he seemed sedate at pick up and the ran over to play with his old preschool (who are smaller and always listen to him), away from his current friends his age, who are mostly bigger than him, and sometimes, he has trouble getting their attention. Plus, he seemed to have been very itchy that day.
The actual causes for him preferring his (literal) old school friends yesterday could actually be anything, obviously, so I backed away from the Cliff of Unhelpful Speculating While You're Mentally Exhausted.
Anyway, this morning, he spontaneously started singing about how he's excited about today.