When Jem loses his pants in the Radley's fence in Chapter Six of Harper Lee's To Kill a Mockingbird, Dill comes to the rescue with a quick explanation. Jem had approached the Radley's back porch in hopes of getting a peek at Boo, but a shadow frightened him and all three kids ran for safety. While crawling through the fence, Jem became entangled and abandoned his pants. When the kids joined the group of neighbors who had gathered after hearing Mr. Radley's warning shotgun blast, Miss Stephanie and Atticus noticed that Jem was in his underwear. It was Dill who interrupted to explain that Jem had lost them "playin' strip poker up yonder by the fishpool." To Miss Rachel, Dill's aunt, this was probably worse than the truth.

"Gamblin' by my fishpool? I'll strip-poker you, sir!"

As Scout pointed out, "Matches were dangerous, but cards were fatal."

To Kill a Mockingbird, by Harper Lee, is set in Maycomb, Georgia, and its primary characters include three children: Jem, Scout, and Dill. On Dill's last night in Maycomb for the summer, he and Jem decide to do something bold.  

Dill and Jem were simply going to peep in the window with the loose shutter to see if they could get a look at Boo Radley, and if I [Scout] didn’t want to go with them I could go straight home and keep my fat flopping mouth shut, that was all.

All three children go, and they encounter some trouble, including a menacing shadow and a gunshot. The children bolt and try to escape.

Jem held the bottom wire; Dill and I rolled through and were halfway to the shelter of the schoolyard’s solitary oak when we sensed that Jem was not with us. We ran back and found him struggling in the fence, kicking his pants off to get loose. He ran to the oak tree in his shorts.

They casually join the crowd of neighbors who have gathered in front of the Radley house to see why the shot was fired. For a short time, the neighbors are talking and no one notices Jem's state of undress. Miss Maudie is the first one to observe Jem's lack of pants, and Atticus is the next. Scout does not think things are looking good for Jem.

It was no use. In his shorts before God and everybody. I sighed.
“Ah—Mr. Finch?”
In the glare from the streetlight, I could see Dill hatching one: his eyes widened, his fat cherub face grew rounder.
“What is it, Dill?” asked Atticus.
“Ah—I won ‘em from him,” he said vaguely.
“Won them? How?”
Dill’s hand sought the back of his head. He brought it forward and across his forehead. “We were playin‘ strip poker up yonder by the fishpool,” he said.
Jem and I relaxed. The neighbors seemed satisfied: they all stiffened. But what was strip poker?
We had no chance to find out: Miss Rachel went off like the town fire siren: “Do-o-o Jee-sus, Dill Harris! Gamblin‘ by my fishpool? I’ll strip-poker you, sir!”
Atticus saved Dill from immediate dismemberment. “Just a minute, Miss Rachel,” he  said. “I’ve never heard of ‘em doing that before. Were you all playing cards?”
Jem fielded Dill’s fly with his eyes shut: “No sir, just with matches.”
I admired my brother. Matches were dangerous, but cards were fatal.

Dill is in trouble with his Aunt Rachel because he imaginatively claims they were playing cards--a scandalous activity among the fine citizens of Maycomb. Even worse, Dill has to claim that the game was strip poker because it is the only thing he can think of which might explain Jem's lack of trousers. Jem tries to mitigate the situation by assuring Miss Rachel that they were playing with matches, rather than cards, something slightly less scandalous than cards, it seems. 

Dill has an active imagination and no aversion to making up stories, but this time it gets him in trouble, though Atticus does manage to calm Miss Rachel down a bit.