The idiom "jumping the shark" was coined in 1985 by Jon Hein in response to a 1977 episode from the fifth season of the American sitcom Happy Days, in which Fonzie (Henry Winkler) jumps over a shark while on water-skis.
The phrase is pejorative and is used to argue that a creative outlet or work appears to be making a misguided attempt at generating new attention or publicity for something that is perceived once to have been widely popular, but is no longer.
I'm not saying Call of Duty is actually jumping the shark here, because we all know the series will continue to be wildly popular for as long as shootin' stuff in games remains fun. And we've already seen Judge Dredd make an appearance as well as Rambo and John McLame. And heck, maybe Vanguard with it's cast of goofy heroes is the perfect landing spot for this, but Snoop Dogg and his arsenal of weapons (the sniper rifle is called The Bong Ripper, the assault rifle the The West Coast Bling, the SMG is Tha Shiznit, and I wish I was joking when I report that each can fire Green Weed Tracer Rounds) makes it seem like they're trying their hardest to strap on some water skis here. Whatever, games are meant to be fun and Snoop will always be relevant so party on y'all.
Besides, it's not like we're talking Godzilla and King Kong are about to trample the map. Huh, what was that latest rumor again...