For a day or two, it was rumoured that Venkatesh lent his voice for a brief time for Dookudu. It turns out that there is no grain of truth in the news. It was said that Venkatesh, as a friendly gesture, could not refuse Sreenu Vaitla's request to dub for some lines in Dookudu.
Since in the past Mahesh Babu had lent his voice for Pawan Kalyan's Jalsa, it was assumed that he has been done a favour by a big hero. That Venky and Vaitla are good friends only helped the rumour to spread fast.
They had been good buddies even before Namo Venkatesa. Mahesh, on his part, would not have minded a big star chipping in if there indeed was any need.