The Avengers would be shocked at first. Tony Stark would probably crack a joke about 'giant naked monsters' while quickly analyzing the threat level. Captain America would be all business, immediately assessing the situation and trying to figure out how to protect civilians. Thor would likely see the Titans as a worthy foe and be eager to engage in battle, swinging his hammer with enthusiasm. Hulk might just charge at the nearest Titan without much thought, seeing them as something to smash.
Mr. Schuester would be in shock. He saw Rachel as one of his star pupils and a driving force in the Glee club. He would struggle with the guilt of not being able to protect her. He would try to keep the club going as a way to honor her memory, but it would be very difficult for him. He might also start a scholarship fund in Rachel's name for future Glee club members.
The Teen Titans would react with a combination of fear and courage. Starfire, being from another planet, might have some knowledge about the invaders which could be useful. But she'd also be worried about her new home, Earth. Cyborg would probably be excited to take on the new technology of the aliens, seeing it as a challenge to improve his own. Raven, on the other hand, would be more cautious and try to sense any dark motives behind the invasion.
Robin would probably be very hurt. He might initially go into a state of shock and disbelief. After that, he could try to find evidence to prove his innocence. For instance, he might search for surveillance footage or eyewitnesses.
Some friends might be shocked at first. Kurt could be overly dramatic, worrying about how this will change everything. Finn might be a bit jealous or concerned for Rachel. Quinn could have a complex reaction, since she has her own history with Puck. But overall, most of their friends would probably come around and offer support, like helping with baby preparations or just being there to listen.
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.
On the other hand, she might try to be the bigger person. She could accept the break - up gracefully and focus on self - improvement. Maybe she starts taking up new hobbies or focusing more on her career or studies in the fanfic, using the break - up as a chance to grow and become a better version of herself.
Sometimes, Rachel could react by using her talent as a weapon against the bullies. She might sing a song that expresses her feelings of being bullied, hoping to make the bullies realize their actions are cruel. She could also turn to her friends in the glee club for support. If Finn or Kurt or Mercedes are around, she would likely confide in them and ask for their help in dealing with the bullies.
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.
Starfire would be overjoyed. She's always been the emotional and positive one. She would probably throw a huge celebration for them, with lots of alien delicacies and bright decorations. She might also give them some advice about love based on her own experiences with Robin.