Dd1 has always been tall and skinny--always very top of the charts tall, but stayed around 33rd percentile for weight after starting solids (before that she was between 50th and 75th for weight, and around age 2 moved back to that area). Everyone always exclaimed over how tall she was for her age, and she never had any "chub" on her. It's just the way she's built! When she dropped those percentiles around 9 months, the nurse practitioner at our ped's office told me "Breastmilk just isn't fatty enough; put butter on all of her food."
I knew better and made sure we focused on nursing before offering food, limiting distractions when she went through phases of not wanting to nurse because she was busy looking around, etc. She followed her own curve, even if it fluctuated around percentiles! On the "weight-for-height" chart, she's pretty much off the bottom, even when her weight is closer to 75th percentile! She eats like a horse a lot of the time and nursed until 2.5. I can't change her body type!
Dd2, on the other hand, is very tall but has been 1-1.5 lbs over dd1's weight from birth to 4 months, which puts her higher up on the weight charts too. It's funny now to see that a single pound makes such a huge difference in what percentile she's in!