“I think they picked me for my motivational skills. Everyone always says they have to work twice as hard when I’m around!” is a jocular line. The saying originated on the American animated sitcom The Simpsons. Homer Simpson said:
 
“I think Mr. Smithers picked me for my motivational skills.  Everyone always says they have to work twice as hard when I’m around!”
 
The line was cited in the newsgroup alt.tv.simpsons in 1998.
   
   
Google Groups: alt.tv.simpsons
Favorite Homer line
Brad Bizzolt
9/27/98
(...)
I usually don’t contribute to these “Character X’s Best Line” dilly-o’s, but I just remembered one of my favourite of Homer’s:
 
“I think Mr. Smithers picked me for my motivational skills.  Everyone always says they have to work twice as hard when I’m around!”
     
Google Groups: alt.fan.blade-runner
OT: regarding Face/Off…
StainlessSteelRat
11/28/02
(...)
“I think Mr. Smithers picked me for my motivational skills. Everyone always says they have to work twice as hard when I’m around!”      —
Homer Simpson
 
29 April 2005, Denver (CO) Post, “Homer and the gang yuk it up for Fox to open sweeps” by Dick Kreck, pg. FF19:
Quotable: ‘I think Mr. Smithers picked me for my motivational skills. Everyone always says they have to work twice as hard when I’m around!’ - Homer Simpson.
 
Google Books
Man Walks into a Bar:
Over 6,000 of the Most Hilarious Jokes, Funniest Insults and Gut-Busting One-Liners
By Stephen Arnott and Mike Haskins
Berkeley, CA: Ulysses Press
2007
Pg. 462:
“I think Mr. Smithers picked me for my motivational skills. Everyone always says they have to work twice as hard when I’m around!” Homer Simpson
 
Google Books
Dim Wit:
The Funniest, Stupidest Things Ever Said
By Rosemarie Jarski
New York, NY: Random House
2008
Pg. 186:
I was picked for my motivational skills. Everyone always says they have to work twice as hard when I’m around.
Homer Simpson
 
Twitter
Mr. Woods
‏@Mr_Woods
“I think Mr Smithers picked me for my motivational skills. Everyone always says they have to work twice as hard when I’m around” - Homer S.
8:25 AM - 13 Apr 2009
 
Twitter
Amanda E. Best
‏@theamandaebest
I’m known for my motivational skills. Everyone always says they have to work twice as hard when I’m around!...lol
3:52 PM - 31 Aug 2009
   
The Telegraph (UK)
Another milestone on Homer’s odd odyssey
As the cartoon nuclear family notch up their 500th episode, there is no sign of a change in the recipe.
By William Langley
7:30AM GMT 19 Feb 2012
(...)
Homer’s delusions may run deep (“I think Smithers picked me for my motivational skills… everyone says they have to work a lot harder when I’m around”), but they don’t extend to imagining that he could last long without Marge and the children.
 
Twitter
FunnyBone
‏@140funquotes
I think they picked me for my motivational skills. Everyone always says they have to work twice as hard when I’m around! !!
7:09 AM - 11 May 2016