But now, with the 5,000-1 outsiders crowned with two games to spare, bookies have turned their attention to Lineker's pants - and they reckon they'll be blue.
The former England striker and Match of the Day presenter tweeted in December that he'd present the programme in his underwear if the Foxes won the Premier League.
But speaking to the Radio Times at the weekend he admitted he had thought he'd be safe: "When I sent the tweet in December I categorically knew there was zero chance that they would win."
As the 2015-16 season unfolded, Leicester fans became aware that something special was happening.  And Gary still seemed to be keen to get his kit off, as he tweeted in March:
And when Spurs drew 2-2 with Chelsea on Monday night, Leicester knew the title was theirs - and that all eyes would be on Gary's undies.
Not too much of a surprise, then, if some people want to hold him to his word.
Twitter users made some suggestions as to what Gary should wear.
Comedian, writer and football fan Matt Lucas suggested a rather cheeky pair of pants, while others were a bit more generous with the material.
In a recent interview with the Independent, Lineker denied ever promising to do the entirety of the programme in his briefs. "I certainly never said anywhere in that tweet that I would do the whole show," he said.
So will the presenter keep his word? We'll have to wait for the start of the new season to see, but we have asked the question...
But someone might be having a punt on polkadots.
When Gary Lineker said he'd present Match of the Day in his underwear if his former team Leicester City won the Premier League, he can't have really thought he'd need to honour that pledge.