Scopely and Telltale Games are teaming up for a limited time event which will be revolving around some of the characters from The Walking Dead Season 1 series from Telltale Games. Some characters involved include Kenny, Lee, and Clementine, all of which will have new storylines for players to check out.
Puzzle & Dragons from GungHo Entertainment gets a lot of collaborations (Rovio, Hello Kitty, etc), which is when another game and its characters show up in this game. The newest one happens to be with Square Enix and their Final Fantasy games. Yes, this means the entire franchise and not just one game in it.
DeNA and Square Enix have announced today that they will be doing a cross-over event with Final Fantasy: Record Keeper and Final Fantasy XIV which will start next month. Final Fantasy: Record Keeper will be featuring the more popular content from the MMORPG during the cross-over event.