My Sister, the Toddler

Smartypants recently learned the word toddler.  Now, she refuses to call her sister anything else.

"Daddy," she says, "where is the toddler?"

"Daddy, can I play with the toddler now?"

"Baby sister, do you know you're a toddler?  Come here toddler.  Play with me toddler."

It's all rather amusing.  Of course, Smiley disagrees and says, "I a baby."  I've tried to convince her she's no longer a baby, but she won't listen.  In any case, she answers to toddler, so I guess that's an improvement.

Maybe I'll teach Smiley to call her sister a '4-year-old Smartypants'.  Or is that derogatory?