Yes. Perfect. Sugreev. Bang on target. That was my answer and with the same reasoning. We can say that all the characters were there common in both Treta and Dwapar stories (whether met or did not meet Ram/Krishna) - they had some role to play in both eras as per reference in Ramayan and MB along with other sources of Krishna. And I haven't taken into consideration Van Parva Ramayan story in Mahabharat but actual Dwapar story in Mahabharat, Vishnu Puran, Harivansh, Bhagwat, etc.
Your turn. Or Varaali can post the next question if you don't.
Vibhishan - Ram's friend in Ramayan and sent gifts to Yudhishthir in Rajsuya yagna (A passing reference in Mahabharat). Since he was Chiranjeevi and was from South and also is mentioned as Rakshas in that part of MB, we have to presume that he must be same Vibhishan.
Jambuvan - Ram's follower and Krishna's father in law
Dwivid - Ram's army soldier and Krishna's enemy in Paundrak's team
Hanumanji - Ram's devotee and met various Dwapar characters in story of Krishna (and even Krishna)
Mahadev - Rameshwaram exchange of devotion and boons/weapons given to Ravan and darshan or boons given to Kalyavan's sage father, Arjun and Jayadrath and Krishna's worship of Mahadev, Banasur battle
Narad - Curse of Ram-Sita separation and various passing visits in both the epics meeting different characters
Durvasa - Lakshman's banishing and Kunti's boon and Pandava's exile
Parshuram - Sita swayamvar and teachings to Bhishma, Drona, Karna
Indra - Flashback tales of king Sagar, Ahalya, Agatsya & childhood of Indrajeet, Story of Sharbhang, Chariot given to Ramji and Govardhanleela, Divyastras to Arjun, Shaktiastra to Karna
Vishwakarma - Golden Lanka, Dwarka, Indraprastha.
Sugreev - When Ram went back to his abode, Sugreev accompanied him along with many others like Sumantra and regained his original form.
Originally I had written Maind instead of Sugreev but strangely I found one google reference that Balram killed both Maind and Dwivid and hence had to modify the question. I had sage Vashisth (Kulguru of Ayodhya and Curse story of Ganga and Vasus in the story of Shantanu of Adi parva) and sage Bhardwaj (Ayodhya kand Prayag saint and Drona's father) in mind too. The names were same but I was not sure whether they were the same or not (And evidence was not as strong as that in Vibhishan and Dwivid) so I skipped them. And all of Varaali's points were also spot on wrt connection with Ram along with Vishwakarma's indirect association I hinted.
Edited by ShivangBuch - 12 January 2012 at 4:51am