What is going on next door?

The gleeful cries and exultation of children were surprisingly heard by me Monday morning while unpacking in my new apartment. As I gazed out my new study window I saw a gaggle of children. Unfortunately, they also saw me, standing there in my boxers. I'm pretty sure that's illegal in California.

"What the hell were so many children doing in my neighbor's house?" I thought as I ran to note the need for a curtain in the study. Really, there are only three or four logical reasons. I consider myself a son of logic, a half-breed mixture of Spock and Holmes (imagine the cool hand gesture w/ the awesome hat). This was a case I could solve.