Ross would have a mixture of emotions. He still has feelings for Rachel, so it would be tough for him, but he'd also want to be there for his friends. Phoebe would be over the moon and would probably start knitting baby clothes right away. Chandler would find the whole situation hilarious and would constantly tease Joey about impending fatherhood. Monica would be the most helpful, giving Rachel advice on pregnancy and making sure Joey is prepared for the responsibilities of being a dad.
Ross would probably be really shocked and a bit jealous at first. He might have a hard time accepting it. Phoebe would be super excited and would probably offer to be like a spiritual guide for the baby. Chandler would make a lot of jokes about it, but deep down he'd be happy for them. Monica would be practical and start planning things like baby showers and making sure Rachel has all the right things for the pregnancy.
Their friends could have a wide range of reactions. Some might be overjoyed and offer lots of support, like bringing over baby clothes and offering to babysit in the future. Others might be a bit more skeptical, especially if Blaine and Rachel's relationship has been a bit rocky before. They could worry that the couple isn't ready for this big step.
Some friends might be overjoyed. For instance, Stiles could be really excited and start making all kinds of plans for the baby shower. He might also be a bit overprotective, constantly checking in on Lydia and making sure she's taking care of herself.
Well, Serena would probably be over the moon. She's always been close to both Dan and Blair and would see this as a wonderful union. She'd be there for Blair during the pregnancy, helping her with shopping for baby clothes and giving her advice. Nate, on the other hand, would be more practical. He'd offer to help Dan with any financial or housing arrangements they need to make for the baby. And then there are the more catty friends, like Penelope and Hazel, who might be jealous and make snide remarks about how Dan and Blair got pregnant so quickly, but deep down they're just envious of their relationship.
They would probably become more awkward around each other at first. Joey might be less of his usual flirty self, and Rachel could be more reserved. Their friendship would be strained as they try to figure out what it all means.
Grover would be super excited. He'd probably start bleating happily and immediately start thinking about all the great food he could eat at the wedding. Jason would be very supportive and offer his help in any way he could, like with security for the big day. Piper would be thrilled and would probably start planning Annabeth's bachelorette party right away. Leo might crack some jokes about Percy finally tying the knot but deep down he'd be really happy for them.
Nami would probably be shocked at first. She might worry about how this would affect Luffy's journey to become Pirate King. But then she would likely start thinking about practical things like how to take care of the baby on the ship. Sanji would be over the moon, seeing it as an opportunity to cook for a new little life. He might also be a bit jealous that it's Luffy and not him having a baby with Hancock.
There could be friends who are initially shocked. They might not have expected Ichigo and Senna to start a family so soon. But after the initial surprise, they would come around and offer their congratulations. Maybe they would even share their own experiences of having children or being around pregnant friends.
Their friends would likely be very excited. For example, Yun would probably be all about making sure Yona has the proper nutrition during her pregnancy. He'd be researching all kinds of herbs and foods that are good for her. Jae - ha might be a bit more teasing towards Hak, but also very protective of Yona. And Zeno would probably just be happy and offer his simple but warm support.
Naruto's friends like Sakura and Kakashi might be initially shocked. Sakura, as a medical ninja, would offer her medical expertise to help Cana during the pregnancy. Kakashi would probably be more reserved but offer his wisdom and protection. On Cana's side, her friends from her own world might be skeptical of Naruto at first, but as they see how much he cares for Cana, they start to accept him.
Harry and Ron would likely be very shocked and concerned. They know Fenrir is a dangerous werewolf, and they might not understand how Hermione got into this situation. They would probably try to persuade Hermione to leave Fenrir at first.