(bound form used in 忙碌[mang2 lu4], 勞碌|劳碌[lao2 lu4], 庸碌[yong1 lu4] etc)
碌
=
石
+
录
:
Lenny Lemur (lu) is keeping a diary (录) in the space station's bathroom (Ø4), but it is quite laborious (碌) to write down (碌) a new entry because it is just a big stone (石).