According to the official website, PonyCanyon is perplexed by a parody of Shinryaku! Ika Musume in the extra short anime of Toaru Majutsu no Index II included in the first volume of the Blu-ray and DVD. Geneon, the producer of Index, hasn't obtained a permission from PonyCanyon, the producer of Ika Musume. In the short anime, Index speaks with "Geso" desinence and extends tentacles.

Screenshot of Index-tan II

PonyCanyon said they take the parody as a fan-service out of good intentions, but insisted that some of the Ika Musume staff were hurt by the unauthorized parody.

Update
PonyCanyon producer Ishiguro Tatsuya removed the post about the parody from the official blog and apologized for provoking unwanted antagonism between the fans of the two anime. He said the investigation of the issue will be conducted between the two sides, not in public.

Source: Ikamusume official website