Alexa and Katie both make a reference to thinking/hoping Harry Styles (born in 1994) secretly wants to marry them. Harry Styles is a singer (One Direction member and now also solo artist), songwriter (he has written all the songs of his solo album, a lot of songs for One Direction and many songs for other artists, for example Ariana Grande) and actor (he had a big role in a Christopher Nolan movie called Dunkirk).
When Dylan asks if Alexa is a superhero as a sarcastic answer question this may be referencing to Paris Berelc's previous role in the Disney XD series "Mighty Med" (2013-2015) starring her as superhero, Sylar Storm.