This joke makes fun of the parity between 'space', as in the invisible character between words, and 'space', as in the void between astronomical bodies. In this case, it is said that the word 'space' was never meant to be there at all, but it was included as a word due to a formatting error.
Oooohhhh, now I get it!
Maybe they should stick to science jokes and leave the English jokes to another cartoon
I must be one of the few who have never found this comic funny, even when it's a science joke.
Yes, you're a very special snowflake, different from all the rest.