Oh good grief... it'd take me a whole day if I had to list them all. Not to mention having to watch them over again.
I'll skip the ones that's already mentioned in this thread, and obvious and repetitous references to Keroro Gunso and Top of Nerae! Gunbuster BGM reused.
Originally Posted by PirateSkittles
The opening sequence for every episode is a direct quote from opening sequence of Kaibutsu-kun
anime series of the 80s.
As for the mayonnaise bit, it's not a particulary "anime" thing.
There's set of people in Japan that likes to eat everything with mayonnaise, and they are called "mayolers" by others.
There are tons of 70s and 80s Japanese cultural references.
Originally Posted by Claies
In the above spoiler tag for ep4.