Programming :: Shell Script - Appending File1 To End Of File2

I'm working on some code where I have two files. I know I can use cat file1 >> file2 to append file1 to the end of file2. What I was wondering is how I could append the first line of file 1 to the end of the first line of file2, then the second line, and so forth.

So if file1 was :
cat
dog
mouse

file2:
orange
red
blue

I want file2 to be:
orange cat
red dog
blue mouse

Also I need it to remove any duplicates from the same horizontal line.