In this comic from 1948, the joke is clear, but the term “somebody call the wagon” isn’t. What does wagon refer to?
A quick internet search isn’t much help: “In Irish slang, the term “wagon” is commonly used to refer to an individual, typically a woman, who is perceived as being overly flirtatious or promiscuous.”
Comics I Don't Understand 
The ‘paddy wagon’? Perhaps to haul him off to the ‘loony bin’? (Sorry if these terms offend, but we’re talking about a 1948 comic here.)
I think Stan has it. Call the wagon to have him taken to the asylum as he is clearly insane.
They think Dagwood is drunk, at 9AM. He needs to be put back “on the wagon”.
I’d presume it’s the wagon to take Dagwood to the “funny farm” (where life is beautiful all the time)…
Like this: https://www.modelcarsmag.com/forums/uploads/monthly_2022_10/2.jpg.7eea7a510baaaa8150aed7dfa2ee2faf.jpg
I don’t see why Stan’s terms should offend, but he’s right. Only a nutzoid (or a janitor) would be pushing a vacuum around the office.
‘Paddy wagon’.
Re: #4- Funny to see a reference to the Model Cars Magazine forum…I’m a regular there. :-)