"If you type 'WAIT6502,1' into a Commodore PET with BASIC V2 (1979), it will show the string 'MICROSOFT!' at the top left corner of the screen. Over the commodore logo. Legend has it Bill Gates himself inserted this easter egg 'after he had had an argument with Commodore founder Jack Tramiel', 'just in case Commodore ever tried to claim that the code wasn't from Microsoft'.
Although the deal to sell Microsoft BASIC did not require the Microsoft name to be displayed, Bill Gates had other ideas. Commodore had internally been making changes to Microsoft BASIC version 1.1, but required an update for the PET in 1979 and the delivery of Microsoft BASIC version 2.0 clearly contained an Easter Egg written by Bill Gates.
According to Jim Butterfield “Commodore paid Microsoft an additional fee to write a revision to the original BASIC that they had bought.
Among other things, spaces-in-keywords were changed, zeropage shifted around, and (unknown to Commodore) the WAIT 6502,x joke was inserted.” Although this update affected other computers, the Easter Egg wrote directly to screen RAM at address $8000, and so it seemed that the Commodore PET had been targeted directly.
The Easter Egg exists on the 6502 BASIC on the KIM-1 but also on 6809 (CPU) BASIC and 6800 (CPU) BASIC. Jim Butterfield goes on to say “Shortly after that implementation, I show this to Len Tramiel (Jack Tramiel’s son) at the Commodore booth of a CES show. He was enraged: “We have a machine that’s short of memory space, and the *!$%$ put that kind of stuff in!” The 51 bytes of code were to be removed for subsequent machines, but the 10 bytes required to spell the message remained in the master copy.
I tried it on my emulator and can confirm its there on v2 1978 version lol