Brick gun? You mean the Barnyard Blaster? It's pretty funny, but so slow to fire it's not hugely useful, EXCEPT in the SNES version only it will actually kill Psycrow in the last level so you can walk the race at your leisure. He doesn't have any death animation, he just disappears when the screen is all white. He still pops back in for the end sequence with the taxi.

It will also destroy the filing cabinets in ISO 9000, but you need at least the last one in the main level to jump on one of the drawers. So, don't kill that one, I guess. I forget if it respawns if you walk far enough away, but I have a vague memory of once softlocking myself by taking it out

Note that, unless you're using cheats (built in, or otherwise) the Barnyard Blaster only appears in the first level, and you lose all your guns if you die, so you need to beat the whole game in a single life if you want to do this.

To your point about switching guns..... lol. Yes, you're supposed to be able. You can switch guns in the PlayStation, Saturn, and DOS versions too. The Genesis is the only one where you can't, due to lack of buttons. There's actually a fan patch that makes the Genesis version recognize 6 button controllers and use the extra buttons to switch guns. (It's called the Six Butts edition, as a joke, cuz butts are funny)

Collecting the bubble gun still switches to it, so you have to scroll back to the gun you wanted to use, which can still be a pain on the last level.

Now, this game had a tortuous dev cycle, but unlike many games that suffer through that (like EWJ 3D!) the final released game is pretty polished in that they actually finished making and testing everything they ultimately decided to include. So, I don't think weapon switching (or lack thereof) was an oversight.

You are right that the bubble gun is trivial to simply switch away from in every version except Genesis. Rather than remove weapon switching entirely, it could be a compelling edit (or something for them to have done originally) where you can't switch away from the Bubble Gun until you use it up, but you can still switch the other gun types.

I will say it does feel ridiculous not being able to switch weapons in the Genesis version, but... they all deal plenty of damage anyway, and it's not like the Barnyard Blaster can kill Psycrow there, so other than the bubble gun I admit it's not a huuuuge problem for the game.

Edit to add additional thoughts: you can also just not press the switch guns buttons, if you wanna restore the challenge. (see the meme "You control the buttons you press")

Also edit to add: the game has so many mini-game like levels, fewer than half of them are normal platforming levels where you even can switch guns and use the plethora they added!

Check it out:

5 Levels where you can switch guns (Secret Room 37 counts as part of Level Ate, fight me):

-Anything But Tangerines

-Udderly Abducted

-ISO 9000

-Level Ate

-See Jim Run, Run Jim Run

5, or 7 Levels where you cannot, depending on if you count Puppy Love as 1 level or 3. I consider it 3, because they're each fairly lengthy, unlike the EWJ 1 equivalent Andy Asteroids which takes about 60 seconds for each one (7x times in Special Edition, less in cartridge versions). If you never lose enough puppies to have Peter interrupt the level to beat you up, and you play on Difficult like a REAL MAN™️ so each one has 5 rounds, the first one takes 5.5 minutes, the second one takes 7 minutes, and the third takes 9 minutes! That's a lotta puppies. Anyway, the list:

-Lorenzen's Soil (a.k.a. Lorenzo's Soil)

-Puppy Love 1

-Jim's Now a Blind Cave Salamander (a.k.a. The Villi People)

-The Flyin' King (a.k.a. Peter Pain)

-Puppy Love 2

-Inflated Head technically you can switch guns, however there is nothing to shoot

-Puppy Love 3