Sri Rajagopalaswamy in Mohini thirukolam, Mannargudi
A unique incarnation of the Supreme Lord is His incarnation as Sri Mohini Murti. This incarnation appears (just like many others) to save the demigods, and to delude the demons. The particular instance of Mohini’s incarnation occurs during the churning of the milk ocean. The demigods and demons, after much mutual struggle, managed to obtain the desired nectar from the ocean. The nectar was held in the hands of Sri Dhanvantari (another incarnation of the Supreme Lord). The demons snatched the pot of nectar, and this loss made the demigods morose. They prayed to the Supreme Lord, who pacified them, and then appeared to reposess the nectar for the demigods…
Sri Devaperumal in Jaganmohini thirukolam, Kanchipuram
In many Sri Vaishnava temples, the utsava murti of the Lord is dressed as Mohini, usually during the temple’s annual 10 day celebration (called “brahmotsavam”). The Lord looks paticularly enchanting when dressed in this way, and often, huge crowds turn out to see the Lord dressed as an enchanting woman! In spite of His enchanting beauty, Sri Parasara Bhattar confessed to Lord Ranganatha that even His beauty in a female form could not match that of His consort, Sri Mahalakshmi- whose very form was mercy personified! In some temples, Perumal is dressed to resemble Saraswathi devi, the consort of Lord Brahma. In these instances, the deity is dressed in female form, and holds a veena, and if often seated on a hamsa vahavam (swan carrier). Sri Malayappa Swami of Tirumala gives darshan this way during the annual Brahmotsavam in certain years…
Sri Malayappaswamy in Mohini thirukolam, Tirumala
As the demons fought amongst each other for the nectar, an extraordinarily beautiful young woman appeared before them. All the demons became captivated by the young woman’s beauty and became attached to Her. Now, because the demons were fighting among themselves to possess the nectar, they selected this beautiful woman as a mediator to settle their quarrel. Taking advantage of their weakness in this regard, Mohinī, the incarnation of the Supreme Personality of Godhead, got the demons to promise that whatever decision She might give, they would not refuse to accept it. When the demons made this promise, the beautiful woman, Mohinī-mūrti, had the demigods and demons sit in different lines so that She could distribute the nectar. She knew that the demons were quite unfit to drink the nectar. Therefore, by cheating them She distributed all the nectar to the demigods.
Sri Namperumal in Mohini thirukolam, Sri Rangam
When the demons saw this cheating of Mohinī-mūrti, they remained silent. But one demon, named Rāhu, dressed himself like a demigod and sat down in the line of the demigods. He sat beside the sun and the moon. When the Supreme Personality of Godhead understood how Rāhu was cheating, He immediately cut off the demon’s head. Rāhu, however, had already tasted the nectar, and therefore although his head was severed, he remained alive (his body became Ketu; both Rahu and Ketu are acknowledged as “shadow” planet in Vedic astrology). After the demigods finished drinking the nectar, the Supreme Personality of Godhead assumed His own form, now visible even to the demons.
Sri Parthasarathy Perumal in Mohini thirukolam, Triplicane
The place, the time, the cause, the purpose, the activity and the ambition were all the same for both the demigods and the demons, but the demigods achieved one result and the demons another. Because the demigods are always under the shelter of the dust of the Lord’s lotus feet, they could very easily drink the nectar and get its result. The demons, however, not having sought shelter at the lotus feet of the Lord, were unable to achieve the result they desired.
Excerpted and adapted from: http://srimadbhagavatam.com/