Pack a punch: Collect 3 fuses
1. In spawn
2. In the power room
3. Near widows wine (in office building)

Place them on a bunker door and pap will be opened

Main easter egg: This can be broken down by doing all 3 challenges and gathering 3 keys.

Soul challenge:
Pick up the soul key in spawn and fill up 3 pentagrams around the map
1st location: Near Stamin up (outside spawn)
2nd location: In between the farmhouse and bunker (near a truck)
3rd location: In the farmhouse

Bell challenge:
Tap 3 bells around the map (all take place in the office building)
1st bell: Near jugg in a cubicle
2nd bell: On the desk near the locked off door
3rd bell: In a cubicle in the widows wine room

After all 3 have been rung, you'll be teleported in the farmhouse and you'll have to survive in there for a minute. Once complete, grab the blue key in that room.

Dig pile challenge:
Pick up the shovel near mule (in farmhouse) and find 3 parts of a map
1st location: In the green house near snails pace (outside spawn)
2nd location: on the truck near stamin up
3rd location: In the cubicle near Widows wine

Assemble the map in the farmhouse and go to the middle of the map near cherry where you can dig a dig pile and retrieve the green key

Key locations:
A red key can be found in the pap room
A green key is found in the dig pile
And a blue key can be found in the farmhouse after bell challenge

When you pick up these keys, you can open a box corresponding to their colour to pick up a part.
Red box: Across the original box spawn (outside spawn)
Green box: Is near phd (in a green house)
Blue box: Outside green house near Snails pace

When you've done all that, you can open the garage door in spawn and obtain your prize as well as construct the pipe gun.

(May or may not need to pack a punch it) you can use the pipe gun to also shoot the lock off the door in the office building. In there is the buyable "ending" in the bus... good luck >:)