In the Call of Duty: Black Ops - Cold War campaign mission Redlight, Greenlight, you will find one of the series' longstanding mascots: Bubby, the Burger Town Boy. This animatronic figure is an ordering point for the in-game restaurant, and talks you cheerfully through the menu of "meat... and more meat!" And if you press his button enough times, a grenade launcher drops out of his ass.
In the campaign mission Redlight, Greenlight. if you interact with the Burger Shot boy by pressing the button multiple times, he will eventually poop out an M79 grenade launcher for you to use for the rest of the mission. from r/blackopscoldwar
As the launcher drops, Bubby plays audio saying "it's our most popular choice."
This kind of easter egg, if you'll excuse the pun, is little surprise. Burger Town is one of several strains of dark humour in the Call of Duty series, and beloved to the extent that Activision built one for the first-ever Call of Duty XP fan convention. In-game Burger Town is a kind of jolly parody of the worst excesses of the fast food industry, and the one it's most reminiscent of is Burger King.
In one of those art-meets-life crossovers, by 2015 Call of Duty was so big that Modern Warfare's launch was accompanied by a Burger King promotion, which not only saw various meals rebranded as 'loadouts' (lmao), but one Burger King restaurant being turned into a Burger Town. I have pictorial evidence of this: the king don't lie.
The Burger King is far from Call of Duty's weirdest cameo, but still.
We're still getting to grips with Cold War, but if you're playing along do check out the many classic Activision games hidden around. Meantime push Bubby's buttons, and go large.