Brudder say "boo?"

LO likes to startle or scare people, especially DH and me.  Shortly after we moved here LO started running out of his room in the morning yelling "boo!"  He'd get the biggest kick out of it if we seemed to have been startled.  Many mornings I try to approach his room in a different way to catch  him off guard.  If I say "boo" first, then he always says "didn't scare me!" even if he jumped sky high when I said it.  If I pass his room and go to NB's first, LO "sneaks" out of his room and will try to catch me off guard on our way to breakfast or some place in between.  In any case, brother (LO) says "boo" most mornings.

Somewhere along the way NB started to count on the "boos" and look forward  to them.  It seemed to be something to which he looked forward.  "Brudder say 'boo' in the morning?" became a routine part of his going to bed banter.  If LO was off his game in the morning, NB was upset that no "boo" was said.  More recently, LO has come to realize the NB enjoys the "boos."  Now LO will tell NB "I'll say 'boo' in the morning, alright buddy?"  It's really quite sweet that they've come to enjoy that about each other in the mornings.  So much so that I don't mind continuing the charade of pretending to be startled when LO is sneaking more like an elephant than a ninja.