HI,
my DD 2.1 just loves emptying things and then filling them back up again...she has a big tub of blocks and loves to them empty them, sort them out and then put them back in tub, and then empty again...she also loves arranging the magnetic letters on the fridge into lines (tallest first etc) and then moving back to how they were, and will come invite you to "join in the fun" and will clap hands and giggle when she's done it.
Also, she likes things in their place, in that if cushions are the sofa are moved around, she will say oh no mummy and put them back to how they should be and again invite you to clap hands for a job well done! i think this may be something she has picked up from me as although i am not anal, i do like things in their place 
she doesn't do it all day, but it is pretty regular thing and i just wondered if this was considered "normal" toddler behaviour or something i keep a little eye on??
xx