This pj pattern would be perfect for a baby/toddler still in nappies. When I found this free pattern link for pj bottoms, I just HAD to make a pair with some left over material I had in the cupboard. I could have bought/picked nicer fabric but I wanted to do a test pair first with what I already had "make the most with you've got". The blog post by From An Igloo put this free pattern together and has done a gorgeous job on hers. You really should check it out.
The mini model in these photos is my Lacie and she's 5 (no nappy), but really loves them.
For some really groovy knit fabrics for these kind of pants/pj's, check out Crafty Mumas online store.