As an excel developer in the 90's, this brings up great memories. I wrote the Doom Excel credits in Office 95. I wish I'd had thought of doing this instead. Kudos.
My brain is desperately attempting to recall the sequence of steps to open it. Ctrl + Shift, clicking something in the Help -> About... dialog box, then F5 or something? And/or there was a star-wars scroller in one of other apps, right?
A dev on my team wrote the following Excel 2000 credits (it was a flying carpet-like game). Afaik that was around the time BillG put his foot down and mandated no new credits. Enterprise customers felt these credits were both a sign of wasted engineering time ("you could have fixed x bugs instead!" and wasted disk space. It's logical, but only partly true. Shipping software on CD means a very long stabilization phase. You couldn't really "fix more bugs" because every bug fix had a risk of introducing another one. That means some Office teams would literally complete their work a year before shipping. They'd sit around half-heartedly helping other teams. That's when someone would take time to write credits. These credits were often tightly-optimized C and assembly, taking very little space. The facts couldn't overcome the optics, so that was the end of fun Microsoft credits.