Earlier, it was the successful Tamil films that were made in Telugu. Films like Khaka Khaka, Ghazini, Dhool, Tagore, etc, are just a few examples.
Now, the trend has reversed. More and more Telugu films too are being remade in Tamil. Mahesh's film Pokiri was made in Tamil with Vijay and it was a huge hit.
There was also the remake of Athanokkade, made with Vijay again. Just a couple of days back, it was announced that Happy Days would be made in Tamil along with other languages.
Now, the latest is that Srikant's Operation Duryodhana will be made in Tamil. Kicha is supposed to direct the film and Sundar Satyaraj is said to be part of the team too!