Nepal Visa on Arrival is part of the ANA, Take Me ‘Round the World Trip Report.
Originally I was supposed to go to Bhutan after Nepal. The lack of availability on Drukair, the flag carrier of Bhutan, necessitated the change of going to Bhutan first.
I landed in Kathmandu at 9:45AM with plenty of time to make my 1PM connection. I was told that I still needed to purchase a 1-day visa even if I was in transit. Instead of arguing like I did in Sudan, I paid for the 15-day visa since I was going to need it anyway (see TPOL’s Visa Drama Saga Stories).
It costs $15 per person and multiple currencies are accepted. If you want to pay by credit card, be careful. It showed up as a cash advance on my credit card!
Another requirement is having a photo, something I sometimes carry and sometimes do not. Instead of fumbling through my bag to find one, I said I did not have one. The officer shrugged and copied my passport instead.
After the visa process, I went out of the airport only to go back in. That’s when the fun got going. The power went out intermittently, and the line for Drukair reminded me of my worst airport experience in Calcutta where everything was done by paper and there was no organization.
I could have waited in the line that had no order for an eternity, but decided to implement my usual strategy of going right to the front and pleading ignorance if anyone made a fuss (see Air China Business Chengdu Kathmandu: Sleeping Through Breakfast). No one did. I showed the agent a digital copy of my Bhutan visa and was given my ticket.
One hour after landing I was waiting in the immigration line to exit Nepal. The line was long and took an additional 30 minutes. The reason I kept such a close eye on the time was to see if Ms. TPOL would’ve made it had she stuck to her indirect flight (see Buying Cheaper Tickets at the Airport). If her flight was on time, she would have but it would certainly have been stressful. 
TPOL’s TIP: Visa on arrival works in Nepal, just leave plenty of time to deal with it.
Why would you transit in Nepal???
Johnny come incomplete. I don’t get your question