I never got that. You've got this seemingly commercial ready song for one business, then suddenly their rivals take it over and put their own song at the end. So... how did that happen? Did the Pizza Dinosaur goons take over during recording?
And heck, did the song end up in Mona Pizza's commercials in that state?
I was thinking of a couple of possible reasons earlier today (I swear, I think of the most random things). I'm not overly familiar with the Ware series, so perhaps these may or may not make any sense.
My first theory is that perhaps being a big megacorporation/chain, Pizza Dinosaur would naturally have an easier time getting a commercial or song on the radio. Maybe Joe, wanting to get a Mona Pizza commercial to air, made an agreement with Pizza Dinosaur that P.D. would help Mona Pizza make/air a song on the radio but in return, P.D. gets to openly bash Mona Pizza during the song, boosting their own sales? That could explain why the Mona Pizza parts of the song are so passive compared to Pizza Dinosaur's part.
Another theory is that maybe the entire song is made by Mona Pizza staff, and the Pizza Dinosaur part is deliberately written to ridicule it. After all, why would any company openly state that their product is worse, and that you should only buy it because it's everywhere? Based on hearing the song alone, I'd much rather grab a slice from Mona Pizza, since they describe their ingredients as fresh, and even offer delivery.
Then of course there's the theory that Pizza Dinosaur interrupts the song mid-airing or mid-recording, which is also really likely. I feel like I had a couple of more theories in mind. If I remember, I'll come back and post them.