Seemingly contradictory, these facts reinforce the basic principle that the Supreme Reality is One,Brahma and that the manifestation various Gods are only an aspect of Reality.
One comes across an Avatar of the God meeting up with another as in Rama and Parasurama Avatars.
Arjuna with Krishna constitute the aspects Nara and Narayana, aspects Narayana.
We have Bharata, Lakshmana and Shatrugna existing along with Lord Rama.
You may also notice one God worshiping another, Lord worships Ramanathaswamy in Rameswaram.
Shiva worshiped Vishnu to remove him of the sin of removing Brahma's head.
But in none of these cases one finds the God worshiping Himself, though thee are instances of Ram and Krishna performing Homas for Lord Vishnu.
We find Shiva worshiping His own Form Shiv Ling.
