Denpa Onna to Seishun Otoko, Haiyore! Nyaruko-san Recommendations
Supernatural flavored lovey-dovey-bishoujo-fanfare anime. Sci-fi element is weak and less worthy of mentioning than your average Star Trek. The fun part of Nyaruko-san is obviously not wet tentacles trying to ass-rape random teenage boy, but hot chicks that spout sexy nonsense and wear easy-to-took-off uniform.
They both are anime with hot chick, slight of life, comedy and mild sex sell. But with some extraterrestrial topping. Possibly mark the era that the legendary romance harem like Love Hina is a little bit too boring in normal world setting, so Japan added robots and aliens to them. Now you understand where all those animes came from.
What else is
Crazy, random stuff happens. One has aliens and one talks about aliens. They also have similar character styles.
Both have aliens in them. In Denpa Onna Erio believes she's an alien, but she's not unlike Nyaruko who is.
They have a similarly light mood with a harem-ish cast of weird but cute characters with no real point to the story.
awesome OP and ED songs
unique sense of humor that only smart people appreciate