A popular ghost riddle is:
 
Q: Why do ghosts like to ride in elevators?
A: It lifts their spirits.
 
“Q. Why did the ghosts get in the elevator? A. They wanted to raise their spirits” was cited in a September 1994 newspaper.
 
“Why don’t ghosts like rain?”/“It dampens their spirits” is a similar ghost riddle.
     
           
30 September 1994, The News Journal (Wilmington, DE), “Just for Laughs,” 55 Hours, pg. 13, col. 1: 
Q. Why did the ghosts get in the elevator?
A. They wanted to raise their spirits.
Lauren McGowan, age 9
Wilmington
 
19 December 1994, Indiana (PA) Gazette, “Mighty Funny’s Mini Jokes,” The Mini Page, pg. 3, col. 2:
QL Why did the ghost ride the elevator?
A: To raise his spirits!
(sent in by Stephanie Parker)
 
Google Groups: bit.listserv.dsshe-l
Happy Halloween
Webinger, Ben
10/31/97
(...)
Q: Why did the ghost always take his family for a elevator rides?
A: He wanted to lift their spirits.
 
Google Groups: novell.community.chat
Long thread
.(JavaScript must be enabled to view this email address)
8/29/01
1. An elevator makes ghosts happy because it lifts the spirits.
 
Google Groups: alt.humor.puns
“Puns of the Weak” 08/23/02
Stan Kegel
8/23/02
(...)
An elevator makes ghosts happy because it lifts the spirits (Pun of the Day)
 
Google Groups: alt.humor.puns
Kids Puns of the Weak 11-16-04
Stan Kegel
11/16/04
(...)
An elevator makes ghosts happy because it lifts the spirits. (Tony Thoennes)
   
Google Books
Spooky Creature Riddles
By Janet Nuzum Myers
Illustrated by Bob Ostrom  
New York, NY: Sterling Publishing Company, Inc.
2005
Pg. 13:
Why do ghosts like to ride in elevators?
It raises their spirits.
 
Google Books
Reading is Funny!:
Motivating Kids to Read with Riddles
By Dee Anderson
Chicago, IL: American Library Association
2009
Pg. 127:
Why do ghosts enjoy riding in elevators?
It lifts their “spirits.”
 
Twitter
Patrick Cheng
‏@patach
@betafood “Why do Ghosts like elevators?  CUZ IT LIFTS THE SPIRITS!”
5:04 PM - 6 Feb 2009
 
Twitter
Lana Hand
‏@Magic1523
An elevator makes ghosts happy because it lifts the spirits!
8:46 AM - 9 Sep 2009
 
Twitter
Subway Belconnen
‏@SubwayBelco
“A ghost elevator lifts the spirits”
5:53 PM - 25 Oct 2009
 
Google Groups: tawitsjokes
Halloween jokes
dave’s gmail
11/7/09
(...)
W. Why do ghosts like to ride elevators? A.it raises their spirits.
 
Google Books
101 Amazing Spooky Jokes
By Jack Goldstein
Andrews UK Limited
2013
Pg. ?:
Why do ghosts liketo ride in elevators?
It raises their spirits!