Because 7 ate 9...
Hey Microsoft, why is there no Windows 9? You've given us 7 and 8, and now you're skipping straight to 10?" "Well, to be completely honest, 7 8 9."
A: Put your head through a window and the pane will just disappear!
Ate Something! ("8 something", actually 8.306)
A: Because Robin ate the worms.
Oh, it's 7 past Cesar
Because 7 was mean. Get it?