The bunny hop was a popular dance in the 1950s. This Easter bunny riddle is from at least 1966:
 
Q: What’s the Easter rabbit’s favorite dance?
A: The bunny hop.
 
A slightly different form of the riddle has been cited in print since at least 2007:
 
Q: Why did the Easter bunny go to the dance?
A: To do the bunny hop.
 
Hip-hop is a type of music, but this similar riddle has been cited since at least 2005:
 
Q: What is a rabbit’s favorite dance style?
A: Hip-hop.
 
   
Wikipedia: Bunny hop (dance)
The bunny hop is a novelty dance that was created at Balboa High School in San Francisco in 1952. It is a social mixer dance, sometimes also referred to as a “party” or “dance party” dance.
 
History
The dance has been generally done to Ray Anthony’s big band recording of the song with this name. It was a vocal hit in 1952, and instrumentally re-recorded c. 1958. The song has been re-recorded by others, including musical updates of the style, for example, a Salsa version. Duke Ellington recorded “Bunny Hop Mambo” in 1954. Other popular music of the era is also used, such as “The Glow-Worm.”
       
5 April 1966, Janesville (WI) Daily Gazette, “Bunny Funnies,” pg. 3, col. 4:
What’s the Easter Rabbit’s favorite dance?...the bunny hop.
 
3 April 1980, Lexington (KY) Herald, “Just Kidding,” pg. A-26, col. 5: 
What is a rabbit’s favorite dance?
The BUNNY HOP!
 
10 July 1984, St. Louis (MO) Post-Dispatch, “Jokes By You,” pg. 4F, col. 5:
What is the rabbit’s favorite dance?
A: The bunny hop.
Christy Finnegan
 
5 April 1990, Newsday (Long Island, NY), “Smiles,” Kidsday, pg. ?:
What is a rabbit’s favorite dance?
Joke Answer: The bunny hop. - Steven Verase, Holbrook
 
Google Books
Backyard Beasties:
Jokes to Snake You Smile
By Connie Roop, Peter Roop and Diane L. Burns
Minneapolis, MN: Carolrhoda Books, Inc.
2004
Pg. 7:
Q: What is a rabbit’s favorite dance?
A: The bunny hop.
 
Southern Maryland Online
101 Easter jokes
jazz lady
04-08-2004, 01:40 PM #1
(...)
Q. What is a rabbit’s favorite dance?
A. The Bunny Hop of course.
   
20 February 2005, Sunday Telegraph (Surry Hills, New South Wales), “The Funday Telegraph” by Matt Frilingos, pg. S18:
What is a rabbit’s favourite dance style?
Hip-hop
 
25 September 2005, Sunday Telegraph (Surry Hills, New South Wales), “The Funday Telegraph” by Richard CLune, pg. S17:
What is a rabbit’s favourite dance?
The bunny hop
   
2 April 2007, Liverpool (UK) Echo, “Time Off: Your Jokes,” pg. 22:
Why did the Easter bunny go to the dance?
To do the bunny hop.
 
Twitter
★ Paul Lujan ★‏
@Paul0451
Why did the bunny go to the dance?To do the bunny hop!
12:02 AM - 12 Apr 2009
 
Twitter
FloridaLady‏
@FloridiaLady
Why did the bunny go to the dance?
To do the bunny hop!  Why is a bunny the luckiest animal in the world?
Because it has four rabbit’s feet!
9:30 AM - 4 Apr 2010
 
Google Books
Just Kidding:
Jokes for Kids by Kids
By Robin Earnest
Lulu Publishing (Lulu.com)
2011
Pg. 24:
Q. What is a rabbit’s favorite dance?
A. The bunny hop.