Allu Arjun before starting out his career as an actor got introduced in Megastar's Daddy as a dance student. Later with Arya, he could find separate fans in youth section.
While he is growing as an actor, he again appeared in a Megastar film, Shankar Dada Zindabad. After that except at audio events and other family events, we haven't seen Megastar and Allu Arjun in a film again.
Now, for Sye Raa Narasimha Reddy Allu Arjun is considered for a cameo, it seems. This is said to be a very important small cameo in the film that Surender Reddy wanted a Mega hero to do.
As Allu Arjun is a recognised star, he will be perfect think the team. Ever since the news as come out, Mega fans are unhappy about Bunny a.k.a Allu Arjun's inclusion.
Because of his speeches and behaviour at events, Allu Arjun lost his goodwill among the Mega fans and he is also seen as a competition for Ram Charan.
Hence they feel if someone else from family do the role, that would be better. As off now, there is no confirmation about who will play the role officially, from the team Sye Raa.