Got to 54,000 and change.
TIPS:
The first 4 levels or so, concentrate on killing baddies in twos with a rock.
Later levels, the bonus fruit is worth thousands. It appears after dropping the second rock. Be aware of this and get fruit.
The levels are programmed in a deterministic manner. You'll notice that on level one, the baddie on the top left ghost himself first. This always happens at the same time. Point is, you can come up with a pattern for each level
When in trouble (multiple ghost getting close) do a double pump to slow bad guys. One pump will not slow them up enough and you will get over-run.
Triple inflating under a rock turns baddies into points. Triple inflate them and wait for a chance for a double kill
Just some thoughts.
3 at once is not much batter than 2 at once. {0 rock kill = 0, 1 rock kill = 1000 (+1000), 2 rock kill is 2500 (+1500), 3 rock kill is 4000(+1500)}