A matter of mistaken identity

Mommy woke me up last Saturday night telling me to place Clarissa in the cot. Still daze and half asleep, I just took the child who looked like Christa (due to the clothing) and did just that. The following morning, I took a look at the children's bed and told Mommy, "Doesn't Christa just look more like Clarissa as she gets older?". Mommy said,"That's Clarissa on the bed! You took the wrong one last night. I thought you realised that?!".

I guess the children shared their clothing as they are almost the same size now, except that Clarissa is much slimmer.

What would I do if we ever get to half a dozen children?