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The 70-year-old actor, affectionately called Mithunda, was handed over BJP's flag at the city's iconic Brigade Parade Ground by the party's state election in-charge Kailash Vijayavargiya and state president Dilip Ghosh. West Bengal goes to polls later this month.
"I am proud to be a Bengali. Today, I am proud to share the stage with PM Modi. This is a dream come true for me," Mithunda said, addressing a huge gathering at the Brigade Parade Ground.
"I know you love my dialogues. Here is my new dialogue. I am not a jol dora snake. I am not a beleghora snake. I am a pure cobra. I strike and you will become a photo," the former MP of the state's current ruling Trinamool Congress party said.
UNB had earlier reported that Mithunda would join BJP, which has not yet been able to zero in on its chief ministerial face in West Bengal that share a land border and a common language with Bangladesh.
Experts told UNB in February that Mithunda would be an ideal CM candidate for BJP, "being a fresh yet popular face".
"His induction into BJP will also help the party exploit his 'star power' and larger appeal, given that Trinamool Congress has been roping in many Bengali actors of late," Rita Niyogi, a retired professor, had said.
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"BJP has no doubt scored many defections from the Trinamool Congress, led by firebrand woman Chief Minister Mamata Bannerjee, but it's desperately looking for a CM face in West Bengal. So, Mithunda would be a good bet," Niyogi had said.
Born in Barisal (now in Bangladesh) and brought up in Bengal, Mithunda made his acting debut with the art house drama Mrigayaa in 1976, for which he won his first National Film Award for Best Actor. He was nicknamed the "dancing star" of Bollywood after he played Jimmy in the 1982 film Disco Dancer, a commercially successful film in India and Russia.
He later won two more National Film Awards for his performances in Tahader Katha (1992) and Swami Vivekananda (1998). He has acted in a total of 350 films in his 45-year career.
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Apart from Bollywood, the veteran actor has appeared in regional language films, including Bengali, Hindi, Odia, Bhojpuri, Tamil, Telugu, Kannada, and Punjabi.
Mithunda's name also figures in the Limca Book of Records (the Indian equivalent to the Guinness Book of World Records) for 19 movie releases as lead actor in 1989 and that record still remains unbroken in Bollywood. He also owns Monarch Group, a holding company with interests in the hospitality and educational sectors.