Iamonthemoonandthereisnowheretogetabeer

 Iamonthemoonandthereisnowheretogetabeer.

Thereisnospacebar.

This is a joke that only works in textual form. If you were to say it out loud I suspect that it would not even be comprehensible. The joke is a pun. The jokester is pretending that he has no spacebar on his keyboard, and therefore cannot type spaces in his text. At the same time he is also saying that there is not a bar in outer space, or a space-bar, to put it more succinctly.

I like puns generally, and so I like this a bit, but I have certainly seen better puns than this one as well.