Here's about the best you will be able to do without finding a higher rez version (as Sam suggested), or re-drawing it yourself (using the pen tool). The edges are sharp, but the outline will be "bumpy and lumpy" starting with such low resolution.
With respect to the text, do yourself a favor and just re-type it. There's no point to trying to extract that separately from such a low rez sample.
PS - Click on the in-line forum preview image to get to a higher resolution PNG-24 version with the gray background removed.
Peppamonio - I just saw the link Sam provided to the store selling that image printed on a T-shirt. When I did the work, I didn't realize that it was an image with commercial usage. Because of copyright concerns, ie, I don't have a license to use that image, and I suspect that you don't either, I have removed the image that I posted a few minutes ago. I am not the copyright police, but nor do I want to get involved with, or in the remotest way promote copyright infringement. So, what do you intend to do with the image with the background removed?