He's an unknown alien who is humanoid in appearance except his right side is blue while his left side is green.
They literally crashed into each other but she has to run off for George's opening day. They met again the next day and performed a musical number using the holographic nature zone. Apollo is a musician, just like Judy's last boyfriend and wrote a song called, "You and Me". He took her out to the drive-in movie and they almost kissed before Jane interrupted them looking for Elroy. Apollo went with Judy to find Elroy and helped the group in standing up to Mr. Spacely. As the Jetsons were about to leave he gave Judy a recording demo of his song and promised to visit.