Why are there so many cross-over episodes of One Piece and Toriko?

Question

I've noticed that there has been many cross-over episodes involving One Piece and Toriko.

In fact, Toriko's first episode has One Piece characters in it.

Is there any kind of connection between both of the two series?

Answer 1

Some possible reasons:

• The manga each is based on are run in the same magazine.
• The anime are aired on the same TV channel in Japan on the same day.
• The anime are made by the same company.

Sources:
anime info: http://www.mahou.org/Showtime/?o=ET
manga info: http://en.wikipedia.org/wiki/Weekly_Shounen_Jump#Series

Answer 2

For celebrating the start of Toriko anime, a Special Collaboration with One Piece was made. A 1 hour special serving as Episode 1 of Toriko and Episode 492 for One Piece.

Year later at the 1st anniversary of Toriko and because of the success of the first collaboration, a second Toriko x One Piece Collaboration Special was announced. A 1 hour special serving as Episode 51 of Toriko and Episode 542 of One Piece.

A third collaboration special crossover was aired on April 7th, 2013, titled Dream 9 Toriko x One Piece x Dragon Ball Z Super Collaboration Special. A 1 hour special featuring characters from Toriko, One Piece and Dragon Ball Z and serving as Episode 99 of Toriko and Episode 590 of One Piece.

Source: Here

Answer 3

There are so many collaborations between Toriko and One Piece because both manga-ka, Eechiro Oda and Mitsutoshi Shimabukuro are very good friends and rivals and they decided to make a crossover seens both manga are serialized on the Shonen Jump :D