Shinryaku! Ika Musume, Denpa Onna to Seishun Otoko Recommendations
Both feature mysterious blue haired 'aliens.' Both are comedy.
mysterious blue haired alien girl
moe comedy very light hearted
Both of these anime were very funny and stuck in my mind for a long time. I really enjoyed all of the characters, and the art styles were both very nice. They're good for cheering you up after a long and tiring day, and they both include quirky and memorable characters who you will grow to love.