SM Entertainment started 2015 teasing fans with an upcoming release.

On January 1, 2015, a surprise teaser image was published on SM Entertainment's SMTOWN official website. The post included a lengthy post, but didn't mention who would be making a comeback or a release. There are multiple options, as there are reports of 2015 comeback for EXO and solo debuts from f(x)'s Amber and SHINee's Jonghyun.  

The teaser image features a triangle morphing into ten squares. Korean netizens (online commenters) have spent time trying to guess who could be making a comeback and teaser, and are guessing that it is either Jonghyun's solo debut or an EXO comeback.

Based on the fact that there are ten squares pictured, the same amount as there are EXO members, and the fact that geometric imagery has been closely linked to EXO since debuting, some suggestions guess that it is EXO's comeback.

However, other netizens have pointed out that the triangle turning into a square may be more closely related to SHINee's Jonghyun. The theory is based on the fact that the logo used for fellow SHINee member Taemin's debut was a triangle, and the triangle morphing into a square could represent the shift from one SHINee member's solo debut to the others.

Another theory is that SM Entertainment will confirm both a Taemin and EXO comeback, beginning with the Taemin comeback followed immediately by an EXO comeback.

Some netizens have also wondered whether it hints to a SHINee comeback, now that both Onew and Jonghyun have recovered from ailments that kept the group performing up to their usual standards.

The cryptic teaser message didn't give many hints, but did say that the mystery will be answered on January second when SM Entertainment reveals which artist will be making a comeback or debut.

Despite several issues with members leaving popular idol groups, 2014 was a very successful year for SM Entertainment musically. Debuts by Taemin, Super Junior's Kyuhyun, Red Velvet, and Super Junior -M's Zhoumi were generally well received, and the comebacks of SM Entertainment's idol groups were overwhelmingly successful.