During this short, Homer stumbles into the third dimension by going through the wall behind a bookcase.  All sorts of weird things are floating around in the new universe, including:

1 + 1 = 2

1782¹² + 1841¹² = 1922¹²

734

P = NP

e ^pi = - 1

107

and something that looked like:

P_p0  > 3H₀²   / 8pG

But the most interesting one, which I was first told about by Owen Baker, is a line of twelve alphanumerics that is quite obviously hexadecimal code.  The complete chain is fully visible in only one frame or two.  Although it is not a very good picture, you can see where the hex characters are when they flash green behind Homer in this brief RealVideo clip.  The characters in order are:

46  72  69  6E  6B  20  72  75  6C   65  73  21

If you feel like working this out yourself, fine.  If you want to know what it says without doing any work, click here.

When translated from hex into ASCII code, the message is:

F r i n k   r u l e s !