A great example for obfuscated PlainTeX code. Happy Pi Day!

Happy-Pi-Day.tex

\documentclass{article}
\usepackage{hyperref}
\begin{document}
\texttt% more suitable for this document
This great example for obfuscated Plain\TeX\ code was posted by \href{http://sdh33b.blogspot.com/2010/03/happy-pi-day.html}{Steve in his Code Blog}:
\begin{verbatim}
              \let~\catcode
          ~`z0~`'1~`,2~`q13~`z#
       14~`46zdefq41'~`4113zgdef,q
     QQ41'~`4113zlet,qBB415425'41-P#
    7427,QPPzexpandafterqAA414243'H#H
   42434341542415,qCC41742743'41i-D42#
  434343,qww',zedefw'PPPCPBAyap!,qEE',q
 6641'~`4113zcountdef,QNNzifnum6RR1R20E6
 YY2QAAzadvanceY-RAY1QMMzmultiply6XX3EqS
 S'Ezhskip0.5em,EQJJzjobnameEQmmwE6TT5qj
 j4142x'41zgdefm'42,,EQ!!zglobalE6CC7Eqr
 r41'T41MT41ACT,qHH'C0rXrYC-CrR,qOO'zifx
 mEPjwxEzelsePjmxzfi,qcc'NX<RHNC<0Szelse
  OEzfiAX1PczelseE!AY2zfi,EzedefzJ'J,qv
   v'@,zifxzJvQOO*zfiEqll'NY<RX-Rzhbox
    'c,Plzfi,zttl~`z612qii41h',~`zx0i
     3.14159265358979323846264338327
       950288419716939937510582097
          494459230781640628620
              899...kthxbye
\end{verbatim}

It compiles to:
\begin{verse}{%
              \let~\catcode
          ~`z0~`'1~`,2~`q13~`z#
       14~`46zdefq41'~`4113zgdef,q
     QQ41'~`4113zlet,qBB415425'41-P#
    7427,QPPzexpandafterqAA414243'H#H
   42434341542415,qCC41742743'41i-D42#
  434343,qww',zedefw'PPPCPBAyap!,qEE',q
 6641'~`4113zcountdef,QNNzifnum6RR1R20E6
 YY2QAAzadvanceY-RAY1QMMzmultiply6XX3EqS
 S'Ezhskip0.5em,EQJJzjobnameEQmmwE6TT5qj
 j4142x'41zgdefm'42,,EQ!!zglobalE6CC7Eqr
 r41'T41MT41ACT,qHH'C0rXrYC-CrR,qOO'zifx
 mEPjwxEzelsePjmxzfi,qcc'NX<RHNC<0Szelse
  OEzfiAX1PczelseE!AY2zfi,EzedefzJ'J,qv
   v'@,zifxzJvQOO*zfiEqll'NY<RX-Rzhbox
    'c,Plzfi,zttl~`z612qii41h',~`zx0i
     3.14159265358979323846264338327
       950288419716939937510582097
          494459230781640628620
              899...kth}% Please notice the missing \bye here at the end!
\end{verse}
But wait! There is even an Easter Egg: With  $@$ as jobname, it compiles instead to:
\begin{verse}\makeatletter\def\jobname{@}{%
              \let~\catcode
          ~`z0~`'1~`,2~`q13~`z#
       14~`46zdefq41'~`4113zgdef,q
     QQ41'~`4113zlet,qBB415425'41-P#
    7427,QPPzexpandafterqAA414243'H#H
   42434341542415,qCC41742743'41i-D42#
  434343,qww',zedefw'PPPCPBAyap!,qEE',q
 6641'~`4113zcountdef,QNNzifnum6RR1R20E6
 YY2QAAzadvanceY-RAY1QMMzmultiply6XX3EqS
 S'Ezhskip0.5em,EQJJzjobnameEQmmwE6TT5qj
 j4142x'41zgdefm'42,,EQ!!zglobalE6CC7Eqr
 r41'T41MT41ACT,qHH'C0rXrYC-CrR,qOO'zifx
 mEPjwxEzelsePjmxzfi,qcc'NX<RHNC<0Szelse
  OEzfiAX1PczelseE!AY2zfi,EzedefzJ'J,qv
   v'@,zifxzJvQOO*zfiEqll'NY<RX-Rzhbox
    'c,Plzfi,zttl~`z612qii41h',~`zx0i
     3.14159265358979323846264338327
       950288419716939937510582097
          494459230781640628620
              899...kth}\makeatother
\end{verse}
\end{document}