Can I market something that is used with another product?

I often buy those Pepperidge Farms frozen cakes. They are about 7” square and fit closely in the box. But as you use the cake and slide the tray with the cake out and in a several times the frosting tends to get smeared on the box flaps and then onto the countertop, your hand, etc. A nice glass or plastic cake tray with a lift-off lid would be great but all of them are for large cakes and are a waste of space.

Can I design one and market it as perfect for Pepperidge Farm cakes? I’m surprised they don’t sell one themselves.

Just say that it is perfect for small frozen cakes and confections. That way you bypass the Pepperidge Farm owners while including all other makers of such goodies.

Aren’t those a single serving, or am I doing it wrong?

I can’t think of any reason why you couldn’t do it. I don’t think it would infringe on Pepperidge Farm’s cake patent unless they sold the same thing, which you could easily verify. I’m surprised someone hasn’t already done it, so this may be your road to fame and fortune.

Likely this. Mentioning their specific brand or product, or including their logo on your product, on your packaging or marketing materials, without their permission, would probably lead to some manner of legal action on their part.

Trademark infringement.

Exactly. Pepperidge Farm almost undoubtedly does not have a:

…but they do have trademarks on their brand name and logo, and rights to their “trade dress” (i.e., the color scheme, fonts, style, etc. which they use on their packaging and advertising).

A product, even a complimentary product like the OP’s proposed tray, which used any of Pepperidge Farm’s names, logos, or packaging appearance, without permission, would likely be seen as being deceptive to consumers, and causing confusion as to who is making/marketing that tray.

So, “a perfect tray for popular frozen dessert cakes” is likely fine. “A perfect tray for Pepperidge Farm’s frozen cakes” probably is not.

Remember what happened to the last guy who tried that?

Pepperidge Farm remembers.

You’re right, of course, but I like cake patent better..