The cruelty of that remark about young Chelsea -- who isn't awkward at 12? -- led me to look it up.
Typical of bullies everywhere, Limbaugh now denies he said it, according to Wikipedia:
On November 6, 1992, three days after her father won the elections, when Chelsea was still in braces, Rush Limbaugh said the following on his television show: "Everyone knows the Clintons have a cat; Socks is the White House cat. But did you know there is also a White House dog?"<6><7> He then pointed to a video monitor, which switched to a picture of Chelsea. Limbaugh has claimed that it was a technical error.