Trocadilho

Sometimes when we have a cold we can’t speak clearly
because our voice doesn’t come out as usually. When it
happens we are a little hoarse.

Here goes the pun, then.

A pony was giving a speech in a lecture hall. A man in
the back told him to speak up because he couldn’t hear.
The pony replied:
“You’ll have to excuse me, I’m a little horse”.