Learn Hardcore Russian: Иногда мой план кажется глупым.

In Russian, with verbs like казаться (to seem), быть (to be), становиться (to become), являться, the complement (the “what it seems/is/becomes”) is very often in the instrumental case.

So:

Иногда мой план кажется глупым.
Literally: Sometimes my plan seems *as something stupid.*

Here, глупым is masculine singular instrumental, agreeing with план (masculine singular).

Using nominative глупый after кажется is generally felt as non‑standard or at least much less natural. The “textbook” rule you should follow is:

казаться + instrumental: кажется глупым, кажется странным, кажется хорошим.

Is Иногда мой план кажется глупым the same as Иногда мой план глупый?

They are close in meaning but not identical in nuance.

Иногда мой план глупый.
This is a direct statement about the plan’s quality: Sometimes my plan is stupid. It sounds more categorical/definite.
Иногда мой план кажется глупым.
This adds a nuance of subjective perception or impression: Sometimes my plan *seems stupid (to me / to people).* It can imply doubt, self‑reflection, or that maybe it only looks stupid, but might actually not be.

In conversation, кажется глупым is softer and more self‑reflective than just глупый.

Can I say Иногда мой план кажется глупый instead of глупым?

You will sometimes hear nominative predicates like this in colloquial speech, but for standard, correct Russian, you should use the instrumental:

✅ Иногда мой план кажется глупым.
❌ Иногда мой план кажется глупый. (non‑standard / sounds “off” to most educated speakers)

For learning purposes, treat казаться + instrumental as the rule.

Why is мой план in the nominative case here?

Мой план is the subject of the sentence, so it is in the nominative:

Кто / что кажется глупым? — мой план.
(Who/what seems stupid? — my plan.)

If you add the person to whom it seems stupid, that person will be in the dative:

Иногда мой план кажется мне глупым.
Sometimes my plan seems stupid *to me.*

So:

Subject (what seems) → nominative: мой план
Experiencer (to whom it seems) → dative: мне, ему, ей etc.
Predicate adjective (what it seems like) → instrumental: глупым

How would I explicitly say “Sometimes my plan seems stupid to me”?

You add мне in the dative:

Иногда мой план кажется мне глупым.

Word order can vary, but this is a very natural version. Other acceptable variants include:

Иногда мне мой план кажется глупым.
Мне иногда мой план кажется глупым.

All of them mean that to me the plan sometimes seems stupid.

Can I put иногда in a different place, like Мой план иногда кажется глупым?

Yes. These are all grammatically fine and natural:

Иногда мой план кажется глупым.
Мой план иногда кажется глупым.
Иногда мне мой план кажется глупым.

They differ mainly in rhythm and emphasis, not in basic meaning. Putting иногда at the very end:

Мой план кажется глупым иногда.

is possible but sounds less neutral and more stylistic/expressive, often used for emphasis in spoken language.

What is the difference between кажется and выглядит here?

Both can be translated as “seems”, but they focus on different things.

Кажется = seems / appears (to someone), gives the impression, not limited to visual appearance.
Иногда мой план кажется глупым.
→ Sometimes my plan seems stupid (in general, as an idea).
Выглядит = looks (visually, outwardly).
Иногда мой план выглядит глупым.
→ Sometimes my plan looks stupid (maybe on paper, from the outside).

In your sentence, кажется is better because it talks about the overall impression or judgment, not just how it looks.

What is the perfective form of кажется, and how would the sentence change with it?

The perfective partner of казаться is показаться.

казаться (imperfective) — ongoing, repeated, general:
- Иногда мой план кажется глупым.
  Sometimes my plan seems stupid (from time to time, in general).
показаться (perfective) — a momentary or one‑time act of seeming:
- Мой план показался мне глупым.
  My plan seemed stupid to me (at some specific moment).

Using показаться in the same structure with иногда is unusual; the aspect doesn’t match the idea of regular repetition. So you use кажется with иногда.

Could I drop мой and just say Иногда план кажется глупым?

Yes, you can, but the meaning changes slightly.

Иногда мой план кажется глупым.
You’re talking about your own specific plan.
Иногда план кажется глупым.
This is more general or impersonal: Sometimes a plan seems stupid / Sometimes the plan (in question) seems stupid. The context would have to make clear which plan you mean.

In many personal contexts, Russian speakers do use мой to make it clearly personal and specific.

Why is it мой план and глупым (masculine forms), not моя / глупой etc.?

Because план is a masculine noun, and Russian adjectives and pronouns must agree with the noun in gender, number, and case.

план → masculine, singular, nominative
- мой план (my plan) — мой is masculine, singular, nominative.
Predicate adjective with казаться → instrumental, masculine, singular
- глупым (stupid) — masculine, singular, instrumental, agreeing with план.

If the noun were feminine, the forms would change, e.g.:

идея (idea), feminine:
- Иногда моя идея кажется глупой.
  (моя – fem. nom.; глупой – fem. instr.)