Sega's mascot has been Sonic the Hedgehog since 1991 when he replaced Alex Kidd.
SEGA is the game company who created sonic and all of the characters
No, Sega needs to use all the characters they already have more often, for example, Marine was only in one game, Sonic Rush Adventure, and she was never playable. Sega sometimes forgets about some of the Sonic characters they have.
Sonic
Well, my friend, sending characters to Sega is a wonderful idea! You can start by reaching out to Sega through their official website or social media channels. Remember to share your characters with passion and positivity, and who knows, they may just find a new home in the magical world of Sega!
Jesus
The Sega Genesis has a huge library of hundreds of game titles to choose from. Probably most famous for Sega's flagship character, Sonic the Hedgehog, the Genesis was also home to a huge selection of sports games such as the FIFA and John Madden series.
Perhaps the most famous is Mickey Mouse
Romeo and Juliet
hug
There are many different characters but the most famous is 'Oliver'.
You don't have to ask permission if you aren't making money off of their characters. Just make sure to say that you don't own the characters yourself and that they belong to Sega. Make sure that the artwork is your own (unless you cite it).
You don't unless you are a part of Corporate Sega.