Okay, cards on the table: I've never eaten a bologna sandwich. It's like, the default sandwich, but no one under a certain age has ever eaten one. Weird. I also didn't know what a spiralizer was until just now, so I guess this recipe is a learning experience for both of us.
Process the bologna through a spiralizer fitted with the large triangle-shaped hole attachment. This'll create the bologna “noodles.”
Melt butter in a large nonstick skillet over medium-high. Add spiralized bologna and cook, turning occasionally, for 3 to 5 minutes until browned and slightly crispy. Transfer to a plate lined with paper towels to drain.
Spread mayonnaise evenly on 3 of the bread slices. Top each with 1 cheese slice. Top evenly with the fried bologna, chips, and lettuce. Spread mustard on remaining 3 bread slices and top the sandwiches off.
If you don't have a spiralizer (and I wouldn't be surprised if you didn't), you can totally just cut the bologna up by hand with a knife.