Well it’s not Doug Rattman level graffiti in the back there but it’ll suffice as a parody and a chance to drop references. Speaking of which, the turret is a nod to an old Portal Machinima from 2008. If you haven’t yet played Portal or Portal 2, the last one was released in 2012, so even if you somehow missed the cake references from way back in the time of Portal 1, you’ve had plenty of time to catch up and make sense of the spoilers.
In any case, I’d recommend both Portal and Portal 2, although if you’re the unlucky type that gets motion sickness, turning down the game resolution will probably help. I don’t think there’s been anything official documented on it but loads of people on gaming forums I’ve encountered notice that when you beef up the resolution, it’s easier to get nauseous. In some cases, I’m one of them (I’ve even had to stop using Minecraft texture packs above x64 for safety).