What's that frog doing on that unicycle?
Here is another Internet Explorer meme. I could see two jokes in this one - the first is the usual - internet explorer is responding to seeing the "dat boy" meme about three years after it was invented. This is an insinuation that internet explorer is slow.
The second reason why this is funny is that it is also showing that internet explorer doesn't really understand the meme, basically saying that internet explorer is stupid.
So, to sum it all up, this is a funny meme because it insults internet explorer.