Exhibit a:
So you bid the fine 6♠, before the final pass LHO takes an interest that tells you she has 2 aces before passing without asking. Fortunately 5♦ voidwood was part of the auction.
She now asks and leads the ♥A, her partner virtually shoves the 9♥ up the leader's nose as I play the 10 and she duly gets the ruff. Not how she'd have played the card with 98.
There isn't much else for leader to do at trick 2 though.
Exhibit b: opps are playing strong NT according to their card
1N (announced as 12-14)-P-P and you decide to reopen with a fruity astro 2♣, LHO having been told her strong no trump is thought to be weak now bids 2♦ with KJx, KJx, KQJ32, Qx. We ended up going for 50 and a good score in hearts, 1N makes in comfort with overtricks, so no damage.
Exhibit c:
1N(12-14)-X-P-P
No alerts, the pass simply says "I have no 5 card suit". On their card it says forcing but not alerted as such, and questioning revealed opener didn't think it was forcing.
Opener held AKJx, A98x, 642, Q9 and opted to bid 2♥, and when the doubler doubled this, opener pulled to 2♠ (doubled by doubler's partner).
Kinda OK so far, except responder started to pull the pass card over 1Nx, then made it clear he hadn't seen the double, had a think and passed. I don't know how she divined that partner had 4 spades and 2 hearts rather than the other way round in his zero count. We misdefended and only took 2♠x -1 for 200, but this was still 60% so it didn't cost that much.