T-Rex: Welcome to T-REX'S RIDDLE CORNER! You'll definitely need a giant brain to answer this noggin-stumper!

T-Rex: Say my name and I disappear. WHAT AM I??

Dromiceiomimus: Oh, that's easy. The answer is Mister Mxyzptlk from Superman lore, an imp who can be sent back to his own dimension by tricking him into saying his name backwards.
T-Rex: What? No - that wasn't what I was thinking of! The answer is "silence"! Say "silence" and it goes away!!

Utahraptor: Seems like a good riddle would have just one answer, my friend!
T-Rex: It WAS a good riddle!

T-Rex: It's "say my name and I disappear", not "say my name BACKWARDS and I disappear".
Utahraptor: I'd argue a backwards name is just a version of the original!
T-Rex: Well if THAT'S the way you feel, I'm sure you won't mind me calling you ROTPARHATU from now -

T-Rex: ...on...