Death. Taxes. Pinjarra winning a game you probably thought they'd lose.
Okay, to be fair the Tigers don't go into many (if any) games as underdogs.
But every now and then they'll head into a match with their previous form suggesting they should probably be beaten, and they'll come out of it having reminded everyone they're the cream of the crop.
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It happened in last year's grand final, when they went into the game having only just squeaked by a young Rockingham outfit and most people (based on that performance) were tipping Centrals to win, but Pinjarra took it out convincingly and are now back-to-back reigning premiers.
And it happened again over the weekend.
The Tigers' first three weeks included winning a close shave against Halls Head, a grind-it-out victory over Baldivis and a cruisy yet not overly-prolific win over Waroona.
Meanwhile the Rams had belted Mandurah, South Mandurah and Centrals with their lowest winning margin at 47 points.
So when the two met at Sir Ross McLarty Oval on Saturday, you'd have been well within reason to think Rockingham would come away with a fourth-straight win.
But nope, Pinjarra did what they do in most big games, they won.
Now I'm not here to discredit Rockingham's performance. They charged back into the game when they looked dead in the water at half time, but unfortunately they just came up against a side that knows how to get the job done in these situations.
It's the reason why, even though I tipped the Rams as minor premiers, I'm backing Pinjarra to win a third straight flag.
Come finals time, when you need a team that despite their form can show up when it counts, my money (well, if I had any to spare for betting), will be on the Tigers.