Semi-hidden visual jokes in anime

[Dracula on a bike]

In Project A-ko, in the scene at 38 minutes 14 seconds, there's a sōzu (http://en.wikipedia.org/wiki/Shishi_odoshi) inside of the mecha's cabin.

Any others?

[TAS]

There are others in A-Ko. Like in the space battle at the start some of the missiles are pepsi cans.

[GanChan]

In some series the name of the anime studio finds its way onto a background building....

Homages are popular:

-Lum and Ran appear in the background of a brief planetarium shot in Maison Ikkoku.

-A brief shot in Here Is Greenwood shows the dorm's Anime Club members holding up a picture of Ranma.

[Lego]

Bebop had Bruce Lee posters if that counts...

[Vicserr]

There are others in A-Ko. Like in the space battle at the start some of the missiles are pepsi cans.

Which of course is a homage to the Budweiser can missile in Super Dimension Fortress Macross: Do You Remember Love

[DocWatson]

The first episode of SDF Macross (TV) (http://animeigo.com/Liner/MACROSS.t):

"Among the many buildings that Hikaru demolishes at the end of the episode are Studio Nue, Artland, and the subcontractor Anime Friend -- three of the major studios behind Macross. A 'nue' is a chimera-like creature in Japanese mythology, and the Studio Nue logo on the building was penned by studio cofounder and mechanical designer Miyatake Kazutaka. (Oh, and also watch for Hikaru's infamous first 'kill.')"

More:

• Otaku no Video (http://animeigo.com/Liner/ONV.t)

...and most of the rest of AnimEigo's anime liner notes. See also the Trivia sections in the ANN Encyclpedia's (http://www.animenewsnetwork.com/encyclopedia/) anime and manga entries.