Below is the contents of a text file that begun as a brief April Fools joke, and kept growing. It was used with Yaakov's Perl script and a custom cron job (since lost) to alter the ready message of an HP printer at a place I used to work.

Things to note: The cron job was a hacky affair that had hardcoded probability weights assigned to various lines, and follow-on rules for others, etc. So, for example, "READY" - the correct, standard ready message - would appear about 30% of the time, to make it more confusing when it was different. I think the the many variations of READY made up a total of 50 to 60% of the weighting. Oh, I was subtle...
Then there's the things like the various song lyrics, and the Pong routine, which would always run through in sequence. There might have been a  couple of other little hacks, but those were the main two.

Also, the printer had a two line, 32 character display - thus the odd spacing in some lines, to get things to split correctly at 16 characters.

It's worth mentioning that not a single person at my workplace ever questioned or even mentioned odd printer messages.

Anyway, there's just enough time before this April 1st for you to hack together your own cron job or scheduled task and batch file. Have fun!

"READY",
"READY?",
"READY!",
"READY...",
"REDDY",
"R3ADY",
"STEADY",
"READY-ISH",
"READE",
"READ",
"RE@DY",
"REEDY",
"REDDIT",
"ROADY",
"ROWDY",
"RATTY",
"UNREADY",
"ALMOST READY",
"READY - ARE YOU?",

"READY",
"SET",
"GO!",

"WARP CORE BREACH",
"TOUCH ME",
"SCORE = 3413",
"STEP AWAY",
"SET TO STUN",
"FEED ME",
"NEED MORE SPACE",
"POUR ME A DRINK",
"IN DISTRESS",
"NICE SHIRT",
"NO PRINT FOR YOU",
"RADIATION LEAK",
"HANDS UP",
"PRESS MY BUTTON",
"TAKE ME HOME",
"LOOKS LIKE RAIN",
"NICE HAIR",
"BE GENTLE",
"BE KIND",
"INSERT DISK",
"BUY ME LUNCH",
"DON'T STOP",
"TAKE A BREAK",
"BLACK SABBATH",

"FREEEEEDOOOOMM!",
"I LIVE...",
"BEER'O'CLOCK",
"I HEARD THAT",

"BUKIT NOT FOUND ERRAR",
"DO NOT WANT",
"OH, HAI!"
"KTHXBYE!"

"   LOOK OUT!    HE'S BEHIND YOU!",
"LOOK!           UP IN THE SKY!",
"IS THIS ALL THATTHERE IS?"
"THERE'S NO NEED FOR THAT",
"     IS IT         FRIDAY YET?",
" |   THIS IS NOT         A PIPE."
"WHY MUST I BE A PRINTER IN LOVE?",
"I KNOW WHAT     YOU DID...",
"YOU CAN'T PRINT THAT!",
"YOU WANT ME TO  PRINT WHAT?!!",
"WHERE DID YOU   SAY IT WAS?",
"THIS ISN'T MY   TRUE CALLING.",
"HELLLOOOOOOOOO  ADELAIDE!!!"
"YOU'LL NEVER    CATCH ME!",
"ZZZZZZZ...",
"   THANK YOU,     COME AGAIN",
"D'OH!"
"MMMMMH....      PAPER..."
"I'M WRITING A   NOVEL, YOU KNOW."
"NO MORE PAPER!  I WANT PIE!"
"FETCH ME...     A SHRUBBERY!"
"THAT'S WHAT     SHE SAID",
"NEXT TIME,GADGET...NEXT TIME....",
"WHY WOULD YOU   DO THAT?!",
"HUR STÅR        DET TILL?",
"HEY, CAN YOU    SMELL THAT TOO?",
"I THINK YOU     OUGHT TO KNOW"
"I'M FEELING VERYDEPRESSED..."
"HERE I AM, BRAINTHE SIZE OF A"
"PLANET, AND ALL I DO IS PRINT..."
"BORED NOW..."
"NOOOOOOOOOOOOO!!",

"ERROR: AN ERROR OCCURRED",
"ERROR: PRINTER  NOT FOUND"
"ERR: EXISTENTIAL     ANGST"
"ERROR: THIS IS  NOT AN ERROR"
"ERROR: PUSH ALL BUTTONS TO RESET"
"ERROR: PAPER    UPSIDE DOWN"
"ERROR: PAPER    INSIDE OUT"
"ERROR: PERFORM         A TANGO"
"ERROR: NOT THE  DROIDS YOU SEEK"
"ERROR: I NEED          A HUG"
"ERROR: JOKE IS  GETTING STALE"
"ERROR: BUT IT   WORKED LAST TIME"
"ERROR: WHAT WEREYOU THINKING?!"
"ERROR: WAIT 'TILTHE WEEKEND"
"ERROR: PRINTING        TOMORROW"
"ERROR: NOT FUNNY"
"ERROR: QUE?"
"ERROR: NO, JUST        KIDDING"
"YOU DON'T NEED  TO SEE HIS ID..." 
"THESE AREN'T THEDROIDS YOU WERE"
"LOOKING FOR..."
"PC LOAD LETTER",
"...___... ...___... ...___... ..",
"NO HABLA INGLES"
" OUT OF CHEESE  +++MELONMELON+++",
"I'M SORRY, DAVE,I CAN'T DO THAT.",
"MAUVE ALERT!    MAUVE ALERT!",
"THIS IS NOT A   DAFFODIL!",
"OUT OF BLACK INKUSE BLACK PAPER"

"ERROR: I'M ALL  OUTTA LOVE...",
"WHEN...WILL I...WILL I B FAMOUS?",
"THE FAX MACHINE IS NOT MY LOVER",
"WELL ITSA       AAALL RIIIGHT..."
"JUMPIN'JACKFLASHITSA GAS GAS GAS"  
"DAAAAAAAAY-O....HE SAY DAAAAAY-O",
"LA LA LAH..."
"  LA LA LAH..."
" LA LA *LAH* LA LAAAAAAH!" 
"YOW!            I FEEL GOOD!"
"I KNEW THAT     I WOULD, NOW..."
"NEVER GONNA GIVEYOU UP...",
"NEVER GONNA LET YOU DOWN...",
"RAINING AGAIN...",
"OH NO, IT'S     RAINING AGAIN...",
"IT'S ASTOUNDING...",
"TIME IS FLEETING...",
"MADNESS.........",
"TAKES ITS TOLL.",
"LET'S DO THE    TIME WARP AGAIN!"
"ISTANBUL, NOT   CONSTANTINOPLE",
"THERE ONCE WAS AMAN FROM NANTUKT",
"WHO@@#*^$#ERROR:OBSCENE OVERFLOW"

"PLAYER 1 INSERT COIN TO CONTINUE",
"      PONG      |              |",
"                |-             |",
"                |-             |",
"|-                             |",
"|  -                           |",
"|    -                         |",
"|      -       |                ",
"|        -     |                ",
"|          -   |                ",
"|             -|                ",
"|           -  |                ",
"|         -    |                ",
"|              |        -       ",
"|              |      -         ",
"               ||    -          ",
"               ||  -            ",
"               ||-              ",
"               ||  -            ",
"               ||    -          ",
"               ||      -        ",
"         -     ||               ",
"           -    |              |",
"             -  |              |",
"               -|              |",
"               *|              |",
"                |              |",
"                |              |",
"                |          DAMN|",
"   GAME OVER       PLAYER 1"