Hellboy hated long term stake outs for lots of reasons. They were long. He had to get someone else to take care of his cats. The US Government, being the US Government, set them up in a furnished apartment instead of a hotel which meant that he had to make his bed and wash the dishes on top of working the case. They were boring. There wasn't any cable (another of Uncle Sam's money saving endeavors). They were long.
There was a knock at the door. An unscheduled knock, which meant that the person on the other side wasn't with the B.P.R.D. Hellboy stood, walked quietly and peered out the peephole. Nothing but the door across the hall. That didn't mean much in Hellboy's line of work.
He undid the latch and creaked the door open until he caught a glimpse of...
"Trick or treat!"
...wide eyed children in the store-bought and hand-made regalia of All Hallow's Eve. He smiled broadly and put his gun away before opening the door wider.
"Wow! Neat costume mister! You look just like Hellboy!"
"Hey Liz, look! Trick-or-treaters."
"Really?" She stuck her head out the door. "You guys look awesome! Oh, crap," she'd taken Hellboy's slang term and made it her own at some point, "Hold on, let me get you guys something."
"Holyshit!" said a boy in a ninja costume who's mother probably would have washed his mouth out for that phrase, "He's got a tail too!"
"Hey lemme see! Move! Lemme see!" a sparkly pink fairy poked and pinched her way to the front and almost managed to wrap her fingers around his tail before he tucked it out of sight.
"It moves too!" she squeaked.
Liz returned and started dropping silvery objects into and assortment of plastic buckets and rolled up pillow cases.
"Aw, come on Liz, not-"
"We've got Baby Ruths and granola bars, HB."
"Granola bars are good."
She gave him a look that said, "Grow up. I'll buy you more later." and continued handing them out to resounding choruses of "Thanks!" "Wow! A big one!" "Thank you!"
"Happy Halloween!" Liz called after them as they moved on to the next door.
By the end of the night there wasn't a single Baby Ruth left. Hellboy consoled himself with the fact that there weren't any granola bars either.