What's the origin of the common phrase "I call shenanigans"?

What's the origin of the common phrase "I call shenanigans"? Note that I'm not so much looking for the origin of shenanigans itself, which I expect could easily be found in the OED or something, but when the entire phrase took on a life of its own as an independent construction. Who coined it? When was it first attested? Did anyone make it particular popular?

I've got a use of "call shenanigans" that dates to 1998, and I strongly suspect that, even if it isn't the earliest use, it's the source of the phrase's popularity over the last decade or so.

In "Cow Days," the thirteenth episode of the second season of South Park, the boys are at a carnival playing games which they come to suspect are rigged. Kyle calls shenanigans, which brings Officer Barbrady to investigate. However, the carny allows the boys to win the game when the officer is present, and Kyle retracts his call of shenanigans.

Later in the episode, the boys discover that the prizes they were trying to win are in fact cheap knock-offs, and Kyle formally reinstates his claim of shenanigans. The claim is upheld this time by Officer Barbrady, which gives the townspeople free rein to destroy the carnival with brooms.

Again, this may not be the very first use of the term, but you asked whether anyone had made it particularly popular, and I think this is what did it. I saw the episode when it was new, and I remember quite distinctly thinking that I'd never heard the word shenanigans used that way before—but within days of the airing of that episode, several of my friends were calling shenanigans every chance they got.

The earliest citation from a quick Lexis-Nexis search reveals this one from the 4 Feb 2000 edition of the Lincoln Journal Star:

"I call this shenanigans," Sen. Ed Schrock of Elm Creek said of the opponents' amendment to LB701.

I realize that you're looking for the specific phrase "I call shenanigans", but if you relax your criteria somewhat, you can go back even further. For example, according to an anthology of Mark Twain's letters published in 1920, he once wrote:

Consider them all..guilty (of ‘shenanigan’) until they are proved innocent.

Which is a somewhat more verbose way of calling shenanigans.

And even further back, the San Francisco daily newspaper Spirit of Age wrote the following in their 30 April 1856 issue:

These facts indicate that there is some shenanegan [sic] going on.

As with almost every turn of phrase, the spoken origins probably far predate anything written.

I can't find a use of "call [or declare or claim] shenanigans" earlier than 2002 , but in the March 1990 issue of Spin magazine, Julian Dibbell wrote (emphasis added):

And why wouldn't the media call bullshit on corporate claims of huge losses to the computer underground?

Sometime in the 90s, apparently, someone substituted a harmless word and the rest is forgotten history...