Hello! There was a Pediasure Ad I remember distinctly from the early 2000s that my family and I used to laugh about because of how bad and cheesy it was. I was born in 1997, so I was pretty young when I saw this, but old enough to know it was silly.
I've snooped around Youtube for it with no luck. There is an entry on TV Tropes for "Tastes Like Diabetes" that references this ad, but it doesn't have a link. Here's the TV Tropes quote:
There was a sappy Pediasure commercial from the early 2000's: A young boy tells his mom that his pet baby rabbit is "so small". His mom assures him that with a proper diet, he'll grow soon enough, just like kids. After mom serves the boy some Pediasure, there's a time lapse to (presumably) a few weeks later and sure enough, the boy notes that his rabbit is "getting bigger".
My parents thought it was unintentionally funny because, in the commercial, the kid doesn't like vegetables and drinks pediasure, while the rabbit eats fresh veggies, so it seemed to imply the mom just gave up feeding her kid vegetables and gave it to the rabbit instead, and her kid is stuck drinking pediasure. Also, the phrase "He's so small!" became a catchphrase around our house because they child said it in this very saccharine, fake way: "Heeeeeeee's so smaaaaaall!!!"
I found a Pediasure ad from the early 2000s that has a similar vibe to it, if that helps. This is pretty much the way the rabbit ad looked.
EDIT: Also let me know if this is not the right place for this particular question, because it is somewhat "identified" in that I know it's from pediasure.