It was the first time for the turtles to go up to the surface.. where all the humans live. And Leo being the strict leader he is, mainly due to him just becoming the leader.. he set some rules.

"Alright guys, always listen to me, don't do your own thing, don't make too much noise, and make sure not a single human sees us, if the rules are broken.. Master Splinter will definitely ground us for life.."

They stood on a rooftop, in the middle of the night.