Happy Pi Day!

              \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

There's even an Easter egg (try running with -jobname @).

For those who can't run TeX, the outputs are here and here.