What connects Mudhalvan, Udhaya and Kadal?

There is apparently a connection between Shankar's Mudhalvan, Vijay's Udhaya and Manirathnam's Kadal. The relation dates back to 1999 when AR Rahman composed a slow melodious track for Vairamuthu's lyrics in Mudhalvan. Later, Shankar thought the song would be a speed-breaker decided to keep the song aside and opted for a fresh fast beat song "Uppu Karuvaadu", which later went on to become a chart-buster.

A few years later, it is quite well-known that AR Rahman used the rejected tune in Vijay's movie Udhaya's title track "Pookum Malarai". The latest tidbit is that one of the renowned ex-assistants of Shankar revealed that the rejected lyrics of Mudhalvan has now got a new lease of life with minor alterations to become "Moongil thottam" in Manirathnam's Kadal. The lyrics and picturization have been receiving rave reviews when the Moongil thottam song promo was released yesterday.

This is the striking relationship between Uppu Karuvadu, Pookum Malarai and Moongil Thottam as revealed by this source. Hope Vairamuthu will confirm this interesting web of connections spanning over a decade.