Ladies and gentlemen, it's Telly Monster. Telly is basically Sesame Street's version of a film extra. He is not one of the main stars like Big Bird, Elmo or even Grover. He's just fits into the background. Poor Telly.
This page says "X-ray" at the top. The illustration seems to say a lot more.
The obvious possibility is that this shows an x-ray of Telly's chest revealing that he has a heart, but no ribcage to protect it.
Still, the look on his face tells a different story.
Perhaps it isn't an x-ray at all; rather it's a giant "X" painted across Telly's heart to show either:
A: Telly has no heart
B: Nobody loves Telly, or
C: Telly is not the answer provided by the hundred people surveyed for the "Family Feud"
A, B, and C are ALL better than the possibility that it is a REAL chest x-ray, because without a ribcage you could toss a beach ball at Telly and his chest would explode.