Shinryaku!? Ika Musume

Similarities: Both MC's are creatures with some human-like features. Both MC's found themselves hanging out in some food establishment. Both MC's have a mission on the place they went through. Both MC's can be rather annoying. Both animes have comedy and slice of life. Dissimilarities: The MC in one anime is a half human and half squid and has special abilities, while the other one is just a pesky bird who simply can talk. One anime is set in some tropical seaside beach in southern Japan, while the setting in another anime is in some shopping district in the city. One anime has no mini skirt fanservice, whiled the other anime does have some subtle fanservice in some character's.  read more 

Both of the girls in there respected series want to conquer the world. Each are funny, sad, and Sekai Seifuku also has action as well. 

the two are about strange creatures who want to conquer the plant , but all the times they try , they fail. and teh two are comic series.